Uber took off here easily because existing minicabs were all really really crap. Not just expensive but often rude or incompetent drivers. I would guess a lot of them were unregistered and uninsured and their cars barely road legal.
Black cabs are Better but very expensive and still rip off tourists all the tine by charging without the meter. Even with the meter it was impossible to get any idea how much a trip would cost before you took it. And you needed cash.
Example: One time I got a minicab, it took the guy over half an hour to arrive, then he had to actually find me which took even longer. Then I realised the back seats of the car were full of vomit and he made me ride up front with the windows wide open - it was winter and cold. Then he didn’t know where he was going and got lost and then he charged me £30 for what would have cost £10 on Uber.
Uber, by comparison is great.