Investors keep giving Uber money.
So long as you have people willing to give you money (in the form of loans or investments for ownership) you can keep running at a loss for as long as the money holds out. Investors believe that Uber will _become_ profitable in the future, so they are willing to keep investing to help Uber get there.
When investors no longer feel that Uber has a profitable future, then it will need to get profitable _really fast_ or it will collapse.
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