Ah. We might be talking past each other. Looking back, a number of the advantages I mentioned are inherent in having self-driving cars. But the benefits compound when we have shared self-driving cars.
Example:
Traffic is improved with self-driving cars because most traffic jams are caused by humans. However, traffic is improved even more when carpooling is automated with a shared self-driving fleet.
Shared autonomous cars will become popular as these compounded benefits are realized.