Geographic saturation is the key to network effects and profitability in the ridesharing business. The more drivers Uber or Lyft have in a given region, the faster the pick-up times, the better the customer experience, and the more rider demand — which in turn allows drivers to earn more money, and attracts more drivers to the network.
http://techcrunch.com/2015/06/28/why-your-next-package-will-be-delivered-by-an-uber/
