This is what probably keeps me out of the market for a car rental service too. I realize I'm probably in the minority, but trying to fit three car seats and several adults into an Uber is near impossible. Not to mention of it's a one way trip, what do you do? Carry the seats with you, arrange to get them back on a later date?
Personally, I'd much rather buy a car with this technology, than rent it.
This is a big enough market I'd be surprised if there isn't just a checkbox on the app "Do you want the taxi that responds to be one equipped with (0 / 1 / 2) child car seats?"
Good luck getting states to change their laws anytime soon. Ironically enough, car seats aren’t required on buses not because they aren’t needed, but they would cut off the poor with kids completely from transportation.
Personally, I'd much rather buy a car with this technology, than rent it.