My experience with the company leads me to believe that it is as much a multi-cultural normalization scheme (Request a ride and meet an exotic foreigner today!) as it is a transportation service.
I've used the service here and abroad (France and the U.K.); it is rare to get a driver who is native to the area. Most are recent arrivals and would be helpless without SatNav.
In re your foreigners question in my experience it is very easy for an illegal alien to drive for uber. All he needs is a somewhat similar looking friend or relative to sign up for him.
Then he just drives and pretends to be the legal one. No checking in at the office no fingerprinting no nothing. As Ling as he’s roughly the same color and build he’s got it.
My opinion happens a lot and that’s why many of them drive for so little.