Door hardware is harder than most kinds of smarthome gadget by a substantial margin. Failure has a much higher liability - a failed door (failing open or closed) renders the entire house worthless. Can’t say the same thing about an internet speaker.

I have an electronic door lock and it needs monthly fiddling to stay in alignment, and I need to push the door in to allow it to unlatch. The door system as a whole needs to be fixed here - but if such issues happen for a guest trying to check in, and the door is Airbnb branded - who is gonna get blamed? Even worse - a door that fails to latch for the night, and no one notices…

I think Airbnb has concluded (correctly) that this is a losing game.