But not commercial drivers licenses, or vehicle registration. And their insurance will hang them out to dry when they have a police report that says the driver was operating an illegal taxi service without the proper license. And US states, at least, are increasingly enacting regulations specifically to classify Uber and similar services as a livery service, which is a commercial use, This requires commercial license, as noted above.
Also, apparently, Uber's insurance only covers the passengers, pedestrians, and the other guy's vehicle. Not the Uber drivers's vehicle, which still isn't covered by their own personal insurance while they are driving for a livery service. And Uber's insurance only applies if their driver is at fault. If you get in an accident with an uninsured driver (and about 25% of California's drivers are, last I heard) who is at fault, you can sue the other guy for money he'll never, ever have, but neither Uber's nor their driver's insurance will ever give you a penny.
Insurance is the biggest gotcha on this kind of service. The most likely risk to bite you in the ass. And if it does, odds are, you're bankrupt, at best. Enjoy your cheap, illegal taxi ride, there, butch.