I expect a simple situation where you may want smart bulbs would be setting colour (I could be wrong here....). But I like to have my lights a softer Orange colour later in the evening rather than the soft yellow of Philips Hue's Ambience range of bulbs, so for those locations that I want more of an Orange colour I either have coloured bulbs in lamps / fittings, or Philips Hue Go lamps.
From a more practical point-of-view, and this may not apply to every home, but smart bulbs also offer options to control lights independently of how they have been wired. This can be an advantage both in an existing home owned by the residents, or when renting. You may have 6-8 lights on the same circuit but in certain situations want to turn on only 2-4 of the lights.
Like I alluded to earlier, bulbs can also be used in floor / table-lamp fittings, allowing for similar control over colour and brightness not often available (I expect) in many lamps.
The only smart bulbs I have are LIFX bulbs in the nightstand lamps next to our bedside, My wife and I each have a Pico on a pedestal on each nightstand that is programmed to control the respective lamps and the ceiling fan.
All other devices are smart switches/dimmers (Leviton, Zooz, and Lutron)
Yes, we could control the nightstand lamps with smart plugs, but as you said, we have the Pico to allow dimming so one of us can stay up and read at night.
I use my color smart bulbs to help indicate “alarm” conditions within the house. For example, if any of the leak sensors in the house indicate “wet”, all of the color bulbs turn blue. This makes us aware of the type of problem quickly.
All of our switched fixtures are on smart switches (and dumb bulbs, with one exception), and all of our plug-in fixtures have smart bulbs (Hue in our case). We have an older house, so quite a bit of plug-in lighting.
I ended up with enough color bulbs in the mix to do some occasional holiday-related stuff, but we could definitely live without that - it's not a must-have for us.
What we really like is the CT range -- we keep most bulbs at ~2200 in evening for a very warm white.
The one place we have both smart bulbs and switch is our bathroom -- my wife likes a warm white in there and I prefer a cooler white, so now we can both have what we like. I use a Blue switch directly bound to those 2 Hue bulbs, so even if my HE goes down for any reason, the switch can still control the bulbs directly (just like a dumb setup).
Usually, only one outlet on a duplex receptacle is switched, so if you wanted to you could plug the lamp into the unswitched outlet, and install a smart bulb and a Pico. That is what I did in the bedroom.
This is direct control via Zigbee, and Inovelli switch and the Lighting app, right? I haven't dabbled in that at all. Z-Wave association goes slow with total loss of hub.
I have (10) smart bulbs in my home. They are white lights only. Nine of them are in table lamps, the other is in a floor lamp. They were among the earliest devices that I installed as I built my (then) SmartThings system. I used smart bulbs because they were less expensive than plug-in outlets or wall switches (most of my use cases don't/can't use wall switches anyway) and they produced no visible changes - such as would happen with a plug-in outlet. They have worked flawlessly for years under SmartThings and now with Hubitat.
One of the complaints I've heard about smart bulbs is that people are prone to turn the power off, which disconnects the bulb from the mesh. I've never had this problem as it seems everyone understands that the lights are run by SmartThings/Hubitat AND because I've provided the ability to use Alexa to voice-override just about all of my automations when needed.
In case you're wondering, they are Cree bulbs. I know they have a bad reputation but, as I said previously, they have been flawless for years.
We rent our home, so smart bulbs (zigbee) is our solution for lighting now.
We used to use timers, then wi-fi smart plugs on a couple bulbs in common areas.
With the exception of a GU10 colour capable bulb, our bulbs are all tunable white lights.
Some bulbs are on a schedule, others are voice controlled, a fair number can also be controlled by Ikea buttons paired to my SmartThings hub (Hubitat doesn't support them) and routed to Hubitat via HubiThings Replica.
My wife is visually impaired. so we also have some motion sensors in a few key places to turn lights on when she's going up/down the stairs.
Colour temperature is adjusted to what works best for my wife's eyes.
Most of the light's brightness is controlled via mode lighting or Room Lighting.