What is the purpose of that rule?
Cab drivers are not elite motor-sports professionals, they are blokes driving a an A to B delivery service whose cargo is persons, so these special licenses don't seem to protect consumers much.
London taxi drivers don't have special super pro drivers licenses, they have instead to fill their heads with arcane street knowledge that is rendered worthless by Google Maps. In Milan and Athens a taxi drivers license is a form of heirloom handed down through generations of a family. If you want to buy an Athens taxi license, you take out a mortgage for it.
The purpose of taxi regulation is largely to control who and how many people can participate in order to drive up costs, and profits, and run a closed shop. That's why the methods employed to do so vary so widely.
Uber aren't especially evil, they are taking on a variety of vested interests and in so doing fighting, in a small way, a little bit of corruption.