[jellicle]

The thing you describe as valuable... isn't. The idea of someone who spends Monday in Madrid, Tuesday in NYC, Wednesday in Moscow and can't be bothered with too many apps is just an idea. That person doesn't actually exist. There is zero value to you for Uber serving other random cities around the world that you will never visit.

Serving NYC is easily a large enough market to be successful. Serving a borough would be.