Google has been working on driverless cars for a few years now. The obvious selling point is that the cars will be much safer without a human behind the wheel.
Currently, a car spends 96% of its time idle. Compare that with planes which spend almost their entire lifetime in operation/airborne. Idle planes aren’t making money, and they need to recoup their hefty $120M price tag. There is an unforgiving economic incentive to make sure it is always in use.
The proliferation of driverless cars will have a similar effect. Cars will spend less time idle: why would a household buy 2 (or even 3) cars, when they only need 1? Ride to work, then send the car home to your spouse. Need to go grocery shopping, but your kid also needs a ride to a soccer game? No problem, a driverless car can handle that.