Most of the black cab I have taken have a also a GPS, so that's not like it is an exclusive type choice, and I wonder why people assume so. Even connected GPS are fairly bad at finding the shortest way if it means running in the other direction for a while and that happens quite often in London and Black Cab driver are quite good at making those kind of info just looking at their gps traffic info.
The knowledge is a very useful tool, and in any city, a driver with good local knowledge is what you are looking for, regardless the middleman you use. Technology is only making the trade off of using amateur bearable, and in reality the real value of Uber and others is from the rest of the service provided.
A bit like in your example - if you had to go to the bookstore to load a new book on your reader and it could only hold one book at a time, the technological superiority of even the latest generation of kindle would not make them go pass novelty items. Real value of ebook comes from the rest of the services you get from it and that's the reason why even with the shit reading experience, the first gen kindle was a success.
The anachronism here is the segregation between black cab and minicab in London and the services the legal restrictions on the services they can offer. Although, IMO, that is not nearly as bad in London as people on HN experience in other places in the world. Black cab are meant to hailed on the street, now, without booking, review or other overhead by drunk people and tourists. Some licensing restriction to make sure you get a basic level of service in those circumstances is probably acceptable. If you have time to plan a bit in advance, there is Uber and plenty of competitors that have always been freed from the restrictions.