It's also possible that each company simply lost all the people who knew the watchOS APIs, and the incremental revenue generated wasn't worth hiring for that role again, or trying to convince someone else at the company to add it to their scope.
Perhaps, as well, there was an expectation that Apple would be the one encouraging Uber to maintain and build the app, and give them favorable treatment on the App Store review processes as a way to sweeten that deal... and then when the larger relationships started to become more acrimonious, any ideas here fell by the wayside.
What’s even worse is the ETA they give you before booking the ride. Still better than taxi in general , but that’s a low bar.
I used a "real taxi" a lot in Germany, Poland and CZ before Uber. The best approximate they gave me was "in half an hour" and it usually was more like 45-60 minutes, if it arrived at all. The usual thing to do was to take one passing by, but that got you a terrible smelly car with a ganster driver that overcharged 2x-5x.
Since you mention CZ - the taxi mafia in Prague was especially legendary. Can't thank Uber enough for disrupting that.