Mass transit is unpopular in all but the largest cities in the US because it's seen as the poor person's mode of transport, and the fear that there may be unsavory people on the bus. Mass transit is also tied to a tight schedule. I used to take the city bus to class, and I left my house an hour before I needed to be at class eight miles away, because I had to switch buses and that left me waiting at the second bus stop for half an hour.

A self-driving SOV designed for personal use won't give much advantage over the current model (except maybe fewer accidents), but if it encourages ride sharing and leased autonomous cars, it would be a net saving.