As an example, US has Uber and Lyft and Mexico has Uber and Didi. When someone from Mexico goes to US, they probably wont have Lyft, and someone from the US won’t have Didi. So Uber gets most travellers’ business automatically.

Likewise even though Uber in Japan is (almost) all taxis and not actual Uber drivers, most global tourists have Uber and not something like Go that’s specific to Japan. So they are profiting off almost all the taxi rides from Western visitors.