This is an older article, and Uber apparently denies it, but you can form your own opinion:
Uber's real time car map is fake
Also:
Why your Uber app is lying to you about available cars
Uber: There are no ghost cars in our app
DON’T BE FOOLED BY UBER’S “REAL-TIME” CAR MAP — IT’S NOT REAL
While Uber has “categorically denied claims that its in-app car map does not use real time data to show where drivers are,” researchers Alex Rosenblat and Luke Stark, both researchers at New York think tank Data & Society, beg to differ. More damning than these two testimonies, however, is a statement from an Uber employee, who said called the rider map nothing more than a “screen saver.”
Said the staffer in an email, “The app is simply showing there are partners on the road at the time. This is not a representation of the exact numbers of drivers or their location. This is more of a visual effect letting people know that partners are searching for fares.”