Think Apple. They have enough market share (even if not a majority), and enough brand loyalty, that they don't need to adhere to existing standards if they think they can resist them and use that to their advantage. Think iChat, and compare to the original XMPP google chat. It was trivial to talk to gchat friends on an iPhone, but hard or impossible to talk to friends over iChat from an Android phone. By resisting making iChat open, Apple created an advantage for iPhone users. Eventually Google redoes google chat with Hangouts, and guess what? They close the protocol. Sharing is only beneficial for you if it's reciprocated.
Does Uber have the clout or loyalty to get away with this? I doubt it, especially since the bar for drivers to drive for multiple services is so low. But if the arbitration service was created without provisions to account for this (e.g., you must partake in the system to use it as a provider), it would be trivial for Uber to fill gaps in their coverage through the service while preventing other apps from doing the same with Uber drivers.
It's a common problem between open and closed systems in markets.
Probably called "Google".
On the other hand it is not nearly as difficult to create a new local ride share service as create a new Facebook
Ground transportation is measured in trillions, which is the sort of market size a $70B company is expected to grow into. Uber should be grouped with self-driving cars and the auto industry, not with taxis.
https://www.forbes.com/sites/greatspeculations/2016/09/21/se...
EU got rid of roaming.
There are carriers in the US that offer flat rates in all supported countries (like Google Fi: 135+ countries at time of writing).
I'm based in the US, I lived in Brazil for several months last year. I stayed with Fi, still paid 10$/gb and 20$/month for unlimited voice/text, kept my number, and immediately had data access.
As a side note, Uber was there, and we used it frequently.