- If you can call your car, it can park farther away. Parking is one of the biggest problems with cars in urban areas.
- Instead of calling of your car, you could just call a car. A self driving car and a self driving taxi are pretty similar, but one can run 24hrs and reduce the parking problem more.
- Computers can do things people can't do. Once enough auto-automobiles are out there, there can be autoauto only "features". The same square footage of tarmac might be able to move cars much quicker. Maybe autoautos can handle 200km speeds. Maybe they can cooperate to make traffic smoother. Maybe they can link together like trains to overcome congestion.
There is nothing quite as good as having a car to take you exactly to and from where you want to go. If self driving cars can really mix with human drivers everywhere they may have a nice smooth path to innovate on gradually. Big vision plans for revolutionizing transport are so centralized, so premeditated.
edit: one more thing. self driving cars interact in an interesting way with public/mass trasport, especially if people dont own their own. It may reduce the demand by competing more directly on one hand. OTOH, it will compliment by providing the last-mile component.