For a self-driving company, replacing a lot of drivers servicing some passengers is much better financially than replacing a few drivers servicing many passengers. Pencil it out yourself and you'll see that doing robotaxis is much better than doing robobuses. Plus, have any cities suggested that they would contract out their business driving to an automous company? Has anyone asked the unions to see what they might do about it?

Autonomous buses will come, but only after the approach has fully taken over the taxi market first.