Yeah, that's one big one. It's really anyone with a dependent that has equipment needs (car seats, hockey gear, etc.)

"But, but, you can rent a car with a car seat!"

That response ignores the fact that there are 4 different major categories of car seats, most kids need a specific one at different times of their lives, and if you have multiple kids you need the specific combination of seats. And of course, car seat installation is hard and takes time, even with LATCH, and I wouldn't trust a random Uber driver just handed a seat to install it properly.

A car seat that can be adjusted into different sizes sounds like a minor part of the R&D needed for Ubertopia.

Nah ... Ever met a parent before? Many of them are pretty serious about their car seats and brands.

So buy one car for the 10 years in your life where you have kids that need cars seats and then rent for the other 50 years of your adult life. It wouldn't need to cover literally every use case in the world to have a major impact on the economy.