Or maybe it's because they give cheap subsidized service. What's the long game? How can they keep it cheap and make profit? They can't. Because it's an extremely inefficient endeavour.

I understand your point but I'm not sure it's relevant. Taxis managed to survive for a long time without any artificial money injection, it's probably at a stable equalibrium. Allowing this artificial market to keep growing is just a endorsing a bubble. The bigger it gets the worst the collateral will be when it'll finally collapse.