One reason is the huge amount of work that is needed to provide support for all the specific features and configuration options for non-standard Zigbee devices.
Especially for Ikea remotes, some of these use Zigbee Group Messaging broadcasts that are not supported in HE platform. So here the problem is not in the time and the efforts needed but in a HE system limitation.
Thank You. I'm not sure when the "Libraries Code" popped up, but it was late last night, I had just finished installing a 6 pack of Heineken and didn't even know the Libraries existed.
Anyway, now with the Heineken uninstalled, courtesy of my liver/kidneys, I once again can read English.
You do not want to know what they are posting about you over on the organs.com board. It's some rough stuff... 
Oh no, not again !
I'm interested in this question as well...I'm running Home Assistant on a pi, set it up a while ago for Aqara contact sensors that I could not get to stay on my C-7. Since then I have had better luck w/the Aqara contact sensors, but still the only place they are 100% reliable over many months is on Home Assistant.
@birdslikewires or @kkossev (or anyone smarter than me, which is pretty much anyone) can we get a short summary of the benefits of moving from HA to this integration for support of "difficult (on HE)" devices like Aqara, Xiaomi, etc.
And to confirm - it sounds like this integration only has support for the four devices that @birdslikewires listed in the OP - is that correct?
Thanks for any clarifications for my foggy brain. 
You can run zigbee2mqtt on bare metal Linux, using the distribution of your choice. And without the overhead of the rest of Home Assistant which you may not need.
Thanks, that's clear, and makes sense. I'm only using HA to send devices to HE, so that is a lot of HA stuff that I don't need/care about.
@birdslikewires - assuming you'll be the one to confirm I have this right.
At the moment there's just the four, but Zigbee2MQTT simplifies adding device support a lot. This really does just route the message to the correct driver using the power of child devices, and the driver no longer needs to worry about device configuration or decoding hex from raw Zigbee cluster messages. It just needs to map the reported MQTT values to Hubitat events.
Of course drivers can squeeze out extra value too, such as timing hold and release reports to provide rudimentary level control, but they don't have to. We can just leverage all the hard work of others on the Zigbee side of things.
Now clearly I can't add support for everything Zigbee2MQTT has and the first port of call should always be a direct connection to the Hubitat hub. But when all else fails and the family want to know why the lights don't work AGAIN, this could be the get-out-of-jail card.
I have had a taste of this recently But I was able to add missing features via a custom driver.
Thanks, that answers my question directly.
Okay, it's pretty clear now, thanks
Be careful when making OTA updates for Ikea remotes.
I upgraded the firmware of my 5-button Ikea remote last night and now it can't connect with Z2M anymore. The OTA update process has finished successfully, it is just the Ikea new firmware that doesn't work the same way as in the older versions. If something ain't broke, don't fix it!
I've noticed that one out of the three IKEA E1812 buttons I've been testing still has the crazy battery drain problem. The other two are fine, just thought I'd mention it in case anyone expected things to be all sunshine and roses. 
Thankfully all of my Xiaomi switches and buttons are behaving perfectly. Phew.
It seems happier now that I've put a repeater in the loft.
After a new battery and a few hours it moved itself onto the repeater. Interestingly, none of the Xiaomi devices are using the repeaters, despite the one in the kitchen being much closer to some of the wall switches than the Z2M coordinator.
UPDATE: Nearly 20 days later, it's still happy. I'm very impressed.
Just stumbled into this. It seems this driver was specifically made to help out with Aqara and Ikea devices. Besides 2 SmartThings arrival sensors, ALL the rest of my Zigbee devices are Aqara devices (contact sensors, leak sensors, motion sensors, and a button) or Ikea Tradfri Zigbee outlets or lightbulbs. All of my Zigbee stuff seems to work perfectly fine. I haven't experienced any devices falling off or anything else weird. So, I guess my question is, what benefit would Zigbee2MQTT provide in my case? Or, has Hubitat integrated this recently which is why I have no problems without it?
Absolutely nothing.
Nope, you're just lucky!
Although of little interest to most users MQTT is like a shared ‘database’ of the state of devices and also can be used to control the participating devices, in this example ZigBee.
What this allows is sharing the information between many controllers so not just HA and HE you can add more controllers and indeed devices that attach directly to MQTT that might not yet have a HE driver available. The HE/HA direct route is possibly quicker and easier but it is a private one to one conversation.
With z2m you can force a device to pair with a specific repeater or let it pick whichever it wants. With xiaomi stuff, once they are paired to a repeater they will not reroute themselves if the repeater goes offline.
Interesting, thanks. A couple of my Xiaomi buttons have decided to use the repeaters now.
Particularly happy this one came to its senses.
It's built-in to the web interface on Zigbee2MQTT. In the top row there's a button which says "Map" and that's about it.
Any chance someone could help create a driver for the Ikea Sound Remote Gen 2?
Model: E2123
IKEA Sound Remote Zigbee2MQTT Payloads
Vol+: {"action":"volume_up","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":0,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Vol-: {"action":"volume_down","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":18,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Play Toggle: {"action":"toggle","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":18,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Prev: {"action":"track_previous","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":3,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Next: {"action":"track_next","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":9,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Button1 - single press: {"action":"dots_1_initial_press","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":18,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Button1 - double press: {"action":"dots_1_double_press","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":15,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Button1 - Long press: {"action":"dots_1_long_press","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":12,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Button 2 - single press: {"action":"dots_2_initial_press","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":18,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Button 2 - Long press: {"action":"dots_2_long_press","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":18,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
Button 2 - double press: {"action":"dots_2_double_press","device":{"applicationVersion":16,"dateCode":"20211214","friendlyName":"IKEA Sound Remote","hardwareVersion":1,"ieeeAddr":"0x94deb8fffe989de2","manufacturerID":4476,"manufacturerName":"IKEA of Sweden","model":"E2123","networkAddress":56137,"powerSource":"Battery","softwareBuildID":"1.0.012","stackVersion":103,"type":"EndDevice","zclVersion":3},"linkquality":12,"update":{"installed_version":65554,"latest_version":16777269,"state":"available"},"voltage":0}
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