Re: TFL protecting users?
The five minute wait period is, as far as I can see, an attempt to ensure that private hire vehicles (and that's surely the category into which Uber falls) all play by the same rules.
Black cabs have certain privileges, like plying for trade on the streets, being able to use a taximeter to charge based on distance/time, and being able to drive in bus lanes.
However, in return for that, they have obligations too, including wheelchair accessibility, and the Knowledge.
I think some within TfL view the 'near instant' availablility (or promise of it) within apps like Uber as an end run around the rule about plying for trade on the streets, attempting to grab that market, without shouldering any of the responsibilities that have been associated with it.
It would be interesting, indeed, if TfL were to also propose that the wait period would be waived for vehicles that were certified wheelchair accessible.
It is odd that the concept of balancing rights and responsibilities, so beloved of right wing politicians when it comes to people doesn't seem anywhere near as important to them when it's companies involved.