Bold statement not true. Rider gets the nearest driver. Only at ORTIA they recently started using a queuing system, the longest driver waiting in queue get the trip.
I have been an Uber driver since December 2014. I have only ever gave a bad rating once, or twice, due to rudeness of a rider. Otherwise all my riders gets 5*, including the all the drunks

I don't expect any tip, it's always a pleasant surprise when i received it. I can only count about 3-4 times that I have received a tip. Other riders have offered to buy me a coke/redbull at a garage or a meal at McDonalds whenever they stop there. Always appreciated.
I also use Uber myself a rider from time to time, my rating is 4.5