If you want to set minimum standards for taxi drivers, to ensure the safety of drivers, I am absolutely fine with that.
But anyone who wants to take the test should be able to, and there should be no artificial limit on the numbers.
Worth keeping in mind.
Likewise, the public tends to demand regulation when the cognitive overhead is prohibitive for an individual,[1] bur more economic at scale by a neutral party. The latter is especially efficient ex ante as opposed to ad hoc.
Again, there are multiple views on what is rational, light and efficient depending only on abstraction and completeness.
[1] Eg, when faced with too much choice, under too small a timeframe, with opaque or imperfect information, and costly information processing techniques.
It has much less relevance for a purely call-and-wait service, which is why application to services like Uber is questionable.