Regulations typically distinguish taxis, which can pick up street hails, from car/bus/limo services, which are pre-arranged or pre-scheduled. Bus and limo drivers also "drive people for money" (and even for buses, sometimes charge by distance), but aren't subject to taxi regs.

And that's not an arbitrary distinction: much of the danger and public interest in cans arises from grabbing randos off the street. As car/limo services track that info remotely, they merit correspondingly less regulation.