I suppose you could own a driverless car and have it continuously deployed as an income-producer moving other people when you're not using it. That creates a lot of additional headaches and problems, though. E.g., how to make sure it's always available whenever you decide you want it? Or, will it be safe to leave your items in the car when it's used by others? (I would guess not).
Sort of like how you couldn't open your own payment processor for the few hundred people in your neighborhood today.