For the same reason, I don't think it's fair to compare the average Uber driver salary to a full-time salary. Some Uber drivers work full-time, but I'd guess most don't. Lots probably only work a few hours a week. Uber provides students/parents/anyone with a way to make extra money on the side.
Also, from the article I linked to, 900k US drivers make $13 Billion a year. So $14k-$15k/job/year. When you factor in that many (probably most) Uber drivers are only working part-time, that's significant income from a super flexible job.