Paris has an incredibly strong Taxi union, which has enjoyed it's monopoly for many decades. Uber cars not being unionized means they are taking money from this massive institution. I think, quite simply, it's cronyism.

Also, the 15 minute wait is because the taxis-by-dispatch are inherently slower. Instead of trying to compete, the taxi union pushed hard on Paris and got them to pass the restriction.

Generally, rather than innovating and trying to compete, the taxi companies in the union have taken the much simpler route of attempting to blockade the upstart.