[1] http://www.washingtonpost.com/blogs/innovations/wp/2014/05/2...
[2] http://www.inquisitr.com/2077969/how-much-do-uber-drivers-re...
There are plenty of folks out there that are unable to work 8 contiguous hours. Perhaps they have children, school, or even a part-time job.
If a college student has free time, they can earn cash as a Uber driver, but when they have a final exam, they don't have to work a second. Traditional part-time jobs, like being a barista aren't that flexible, so the alternative may be having no income during college.
Technically, Uber is not "lying" here. They're just talking gross wages, before driving expenses. Cab salaries are lower because the cab companies assume some of the costs of driving and build them into the daily/weekly cab lease fee (keep in mind almost all taxi drivers are independent contractors in the US).
And agreed on your last point. The questions/issues are much larger than Uber, which we bring up at the end of the post. Why are these jobs appealing to people? Maybe they're indicative of more systemic problems, and we should focus our efforts on things like improving the US education system so that more individuals have access to higher paying jobs.