I'm not seeing the answer to my question here.Do you have children you write off? You do, right? That is the almost the only way you would have zero tax liability.
The reason is you have to pay self employment taxes (Minimum) on whatever is left on the schedule C. There are only a few things that offset that number and they are mostly credits (like EIC...people with children make a killing on this).
Many people do not qualify for these credits so we have to write off everything legitimate we can on the Schedule C.
How many years have you filed taxes with Uber as 100% of your income??