I generated my Zigbee graph today. I do understand that this can not be completely relied, but still at a high level, it seems that almost all my end devices(battery based) are directly connected to the hub, instead of going through ay of the so many repeaters. I already tried shutting down the hub for 20 mins and restarting it but the graph got generated similar again.
Any thoughts why none of my sensors are choosing to use the repeaters?
The simple answer is that they think they're direct signal is good enough. The secondary simple answer is they are the types of devices that like to hang onto the first coordinator they see. You could try re-pairing one to see if it kicks over to a repeater. But, without know your home layout, device types, and reported LQI, it's all a guess.
Which hub are you running? What firmware version? If it a fairly recent and you are on a C-8 or C-8 Pro, you can try reducing the power that the hub is using for the Zigbee radio.