Funnily enough UberX wasn't the first. Uber was only using licensed Taxi drives for UberBlack, and wanted to do UberX, but knew they'd be shut down immediately. Then Lyft did it....normal people accepting rides. Uber waited for the Lyft shutdown. Didn't happen. Then the city of SF proposed giving Lyft a licence.

At that point, Uber pulled out the brakes and that changed their view on regulations permanently.

Source---straight from Travis (TK) himself.