Uber has partner drivers which have their own companies, their own rating, and can be punished for their behaviour. Once a company completely vertically integrates (like Google would like), meaning they have their own cars, they no longer want to punish themselves for bad behaviour/cars. Since they have to choose between short term cost of higher maintenance fee or long term cost of loss of quality of service their managers will start to optimize for quarterly results: cutting short term costs. What they want is to first entrench the market, push out competitors, introduce complex regulation and fees which prevents new competitors into the market and then start cutting costs everywhere they can and increase prices.

Since you mention Uber, I can definitely see in my city how the quality of cars decreased and they started using almost inclusively cheap immigrants who realistically couldn't pass a drivers exam in my country and have on multiple occasions driven into wrong directions/ran red lights etc.