Mini cab drivers are often self employed, they pay a "radio fee" for the booking office, provide their own vehicle, licensing etc, have fares set centrally, and they keep their fares (and take cash to avoid paying tax).
On that regard I would say that the court case a little while back about the employment status of uber drivers might have some bearing. IIRC they demanded some drivers be available at certain times, and did other things that put the lie to "self employed" status.
Don't get me wrong, I know all the shady shit that goes on in this direction with delivery drivers etc, and I expect at some point we're going to end up with a big shift in the rules.
With Uber it's just one of many things that I dislike about them.
How is uber any different?