The thing that makes me think of taxis is the the driver cost/total cost ratio is high, so removing the driver is a big deal. Buses and long haul trucks are al

The thing that makes me think of taxis is the the driver cost/total cost ratio is high, so removing the driver is a big deal. Buses and long haul trucks are already pretty highly optimized in that the driver's time is a relatively smaller component of the total cost. Also, the total cost is much lower.