If a passenger is required to have a driver's license, that implies that the passenger takes on some liability for what the vehicle does. That would be a showstopper right there, especially in a vehicle that has no driving controls.

Guess: Until laws catch up, a drivers' license might be needed, techically, to use any robotaxi. But every jurisdiction will be different - both on the legal side, and on the "would they bother to enforce it?" side.