I suspect that as computer driving takes over, there is less need to own any of the "appliance" vehicles, for example camry, metro, cavalier, accord, etc. It will be much cheaper on a total owning and operating cost to order up the computer driven taxi as needed.
Still has some big drawbacks; primarily the inability to do simple things like leave stuff in the car that might be needed the next day.
Remember, the car also functions as a lockbox and privacy area for many people. I've had a few jobs where I couldn't really leave anything at my desk and expect it to be there when I got back, and others where the only way to have a little privacy for a phone call was to go sit in your car.
Sharing also adds a - potentially long, depending on location - delay if you need a car unexpectedly. Not a good thing when you find out your child or spouse is on the way to the ER.