Manually driven groundcars are a terrible idea. They were introduced at a time when attitudes toward safety were very different, and we're used to them now. They kill people all the time; it's an everyday occurrence. When we have some viable alternative, they'll rapidly disappear from the streets.

Manually driven aircraft have sufficiently strict licensing controls that most people don't bother to become trained to operate them, though almost anyone can. The SF aircar fantasy is one of mass ownership, not specialized applications. I can only see that happening in a modern liability and regulatory environment if they're point-and-click simple to operate, and safer than modern cars.