Autonomy is helpful for all transit scales. When I see an essentially empty bus go by, I shudder at the waste. Other times, I cannot use public transit because they stop running to avoid travelling below a reasonable capacity. More frequently, public transport cannot handle first and last mile because it's inefficient. Transport must handle all these problems and the solution is likely a mix of higher- and lower-capacity vehicles working together. A "car" may drive you to a be picked up by a "van" and, for longer trips or during rush hour, on to a "bus", and then, as you get close to your destination, back to a "van" and a "car". There may be less need for large transfer stations and instead they'll be distributed so dynamic inter-vehicle transfers can happen almost anywhere with minimum wait between dropoff and pickup.

The complexity of having all these vehicles work together so dynamically is beyond human capacity, hence the need for an integrated system with extensive autonomy. Yes, a human could and will drive some of these vehicle but the system will work far better with many, most, or nearly all of them being autonomous.