The same reason relatively few people AirBnB their homes. There will be an administration overhead of at least some kind - who cleans the car? What happens when

The same reason relatively few people AirBnB their homes. There will be an administration overhead of at least some kind - who cleans the car? What happens when someone throws up in it? And so on. I'd say, why will people buy their own robotic cars at all? At least in major cities anyway - you could buy a membership to a program (ala ZipCar, car2go, etc) and just have "a car" on tap. The downsides of ownership (maintenance, etc) will be gone.