> All Uber drivers I talk to alternate between Uber and Lyft and exploit any promotions or incentives either firm offers.

This is no different than any other for hire industry though. They are making the choice that best benefits them financially. Uber knows this, lyft knows this, basic economics and human instinct to better their own situation. There will always be more drivers though so I doubt they are concerned about the problem to be honest. The barrier to being an Uber driver is so low.