"anywhere in the world" being the challenging part. If you're think about it from the perspective of a local taxi company, sure, it doesn't make sense. If you're a global service then it's probably different.
The only people who care about being able to use the same app in Bangalore that they do in Palo Alto are Uber investors and a tiny handful of globetrotting Davosians too lazy to install a new app or send an SMS.
edit: removed the royal we