well, I guess my hope is that renting a car whenever needed is cheaper than the cost of purchasing, maintaining, insuring, and storing a personal robocar. It would be quite hard to make the US more car-dependent than it already is! But I am speculating - you may very well be right
It will only be cheaper if you don't drive much anyway, and you are the type who would never be seen in a car more than 3 years old.
If you drive a lot (like the person in the countryside) the car that is there when you want to is worth owning vs a shared car that you might have to wait for. Plus by owning the car you can just leave your golf clubs in the trunk.
If you can stand being in a used car you will discover that shared cars are all more expensive just because at the first sign of cosmetic wear they get rid of it while seats that have been sat in a few times are still good enough for many more years. (unless you almost never drive anyway)
Because of the above I don't see much growth in the shared car market. There will be some because there are people who don't have parking, people who don't drive much, and people who demand a new car that they don't otherwise care about. However the vast majority of people will still own their own car.
Cost is only one dimension of renting a car. As long as the car rental companies keep making it as painful as possible, it won't be a solution for usual usage. Hopefully Waymo goes after them too.
Very much. They often don't have cars at all - despite letting you reserve them. Or they are not open when your train arrives / leaves. I'm considering a 3 day drive my next trip in part because it is the only way to be sure we can get around when there.
(we are going to a remote location where I wouldn't expect public transit to serve, but the train station is in a small town that still should have some transit but doesn't)
