There is a fair bit of overhead that comes with being an Uber driver (gas, maintenance, the cost of the car, additional taxes). So if you are being paid $21 an hour your take home will still be a lot lower than someone being paid $21 an hour in a normal job.
When I was driving, I could make abut $1000 a week when working 60 hours.
$150 of that would be gas
35 would be insurance
15 would be oil changes
$50 per week should be set aside for savings to reinvest into the vehicle in the form of proper maintenance.
the final number, $750 for working 60 hours 12.5/hr
Did you factor in depreciation as well? I would imagine that the additional miles on the vehicle would cause pretty significant depreciation, and would shorten the life of the vehicle, requiring you to buy a new one sooner if you are planning on keeping it until it dies.