This never happened, as much as Uber would like to imagine themselves a grassroots, populist movement.
Uber started out a service that connected black cars/limos to riders. The idea was to provide competition to taxis, and the easiest existing source of professional drivers was limo drivers, who had a great deal of down time between bookings - and Uber helped fill in the gaps and provide extra income.
Uber was never a "connect riders to random people willing to give a lift" - other companies tried this model, most notably Sidecar, though even then I think most of its driver-base were at least semi-profesisonal.
Within the last three months, I've seen short text ads where driving for Uber is marketed as a job that pays $21+/hr.