I think the general answer to this question is deceptively simple, and has two parts: 1) many of the most important regulations are preventative and relate to i

I think the general answer to this question is deceptively simple, and has two parts: 1) many of the most important regulations are preventative and relate to issues that are invisible to the average passenger (driver qualifications and training, insurance, vehicle maintenance, etc.). 2) The harm that many taxi regulations seek to prevent is disproportionate to the disciplining effect on operators of a single poor review. A serious accident, for example, will typically only affect a single rider (or group of riders) who can, at most give a zero-star review. I cannot see how the possibility of a single zero-star review out of hundreds would give a driver any incentive to do anything that costs a significant amount of money -- after all, many Uber drivers probably are used to getting the occasional bad review for no reason at all. Edit: Bonus reason #3 -- Situations may arise where the government wants to prevent driver behavior that many riders will approve of, for example, to protect other drivers and pedestrians. For example, the government might want to use licensing to impose an extra stiff penalty on taxi drivers who violate traffic laws (i.e., license revocation or suspension). Passengers may approve of this sort of behavior if it was intended to get them to their destination faster.