One problem with autonomous/shared driving no one talks about is: trashed vehicles.
Other forms of shared transport have other people with you to keep you (relatively) in line — driver and other passengers. Even so, people still trash busses and BART trains, and still throw up in the backseat of Lyft/Uber cars.
When no one is watching, and it is no one’s car, how will people trash them?
The tragedy of the commons…