[mamon]

Facebook has network effects: you use it because all of your friends are using it, making a cost of switching high. In the ride sharing business however, there is zero consumer loyalty - installing a new app in your phone takes one minute. Riders can have multiple apps and order ride in the one that offers best prices, and all the drivers will probably be using multiple apps already.

Also: you don't need to have "the best app in the market", just a reasonably good one. Advertising cost is more of the issue, but you can do that by starting in one local market, get some market share and use it to attract more VC capital.