Usage of public transit is fundamentally limited by antisocial people.
No one wants to be on the same bus as a black guy going "I'm going to kill this white girl" and then stab you in the neck. No one wants his wife, daughter, mother, etc to be Iryna. No one wants them to be that girl that got burned alive either. Or any other of the countless public transit statistics.
That is the problem with public transit, and that's why it's usage is now suffering in Europe as well.
So that is a whole different problem, completely unrelated to the problem of self driving. Self driving primarily replaces one's own driving. It's not for the people so poor, that they can't escape the antisocials.