And you can tell that they are not Canadians? Is this based on their skin colour?
In order to be exploited by Uber, a driver must be legally entitled to work in Canada. Those could be international students, permanent residents or citizens.
If you look at the whole transportation industry, most drivers are new Canadians.
As with Uber, with a very low bar of entry, it is filled with drivers who are new to Canada and the others are just doing it for other reasons.