As a parent myself who has always had a car but has aspired at times to go car-free, I think the whole "semi-frequent short term car rental" thing only really gets realistic when the kids are old enough to just need those tiny Mifold booster seats / seatbelt adjusters.
Conventional UAS-attached car seats are just too bulky and troublesome to be installing and uninstalling all the time in cars you only rent for a few hours at a time.
