That's not really true though. Their pay is higher to make up the difference.
No, the main thing is that Uber doesn't have to guarantee them fulltime work, or at least any kind of minimum amount of work.
i.e. Uber can say "No work today, too bad".
Citation needed. Please include costs of owning, operating, and maintaining an automobile in your calculations.
I thought part of the problem was that it isn't, in general.
If Uber paid their Social Security and Medicare taxes, then Uber would just lower their base pay, and the net would stay the same. Or in other words the pay is higher because the driver has to pay those taxes.
Generally people do not act as fully rational economic actors, so we can't assume that this is not true based on the fact that people still choose to do it.
Which isn't to say they shouldn't have that option.