usaf importantly doesn’t have any liability in the case of accidental death

Reaction time requirements are probably much more forgiving for drones -- don't need to suddenly brake or change course due to the movements of other tightly packed drones around you during the daily commute

There is also the question of trust, one of the biggest non-technical challenge to overcome would be to convince general public to get into a car which doesn't have a driver. It would be similar to getting into a rollercoaster.

No control whatsoever of what might happen next despite every bit of your trip being pre-planned to the dot.

USAF has billions to throw at the problem.