How can Uber have trouble turning a profit? What expenses do they have? Are they literally wiping their asses with money, or something? I can't imagine how maintaining a few little apps would cost billions of dollars a year.
Here is my thought to answer this question... They reinvest into their business by expanding as much as they can for now. If they can dominate the market all over the world, then they will be able to make a lot of money. I would say it is a smart move in this kind of global business (even though I don't like them).
Currently, it is their preparation time in attempt to expand to every single acre in the world. To do so, they need a lot of money to start up the business in new locations. Thus, they can't turn a profit yet. Once they are ready to make real money, I'm sure they will come up with another strategy to maximize profits (which I don't have an idea yet).