That is a fair point.
With regards to drivers having to have "the knowledge" I consider that more a feature than a bug. I've gotten a few taxis in the last while with drivers relying solely on GPS - including a couple of Hailo drivers - who ended up taking hopelessly circuitous routes, or even got lost altogether.
Agree that the artificial limit of taxis and cost of licence is an issue. You should try getting a taxi in Dublin where there was wholesale deregulation about 15 years ago. You can get a taxi in minutes! Sucked for the drivers at the time though.
I believe in London you also have the option of the "minicab" (here they're called "hackey" cabs) - which is what the Uber business model really augments. All it takes is for those guys to catch up with technology and Uber becomes irrelevant once more. I'd be fairly sure they're up-to-date on the dubious labour practices though /s
As a result, Black Cabs are expensive. The drivers also have a famous tendency for racist rants and their captive audience.
Hailo doesn't do anything to make travel more affordable.