Now that the ideal experience is available, the question is whether people are willing to pay for it.
Right now - it's being paid for (all salaries, etc.) by shareholders as the company runs a massive operating loss.
The question these articles lay out is that - at least in theory - this can't last forever. No one's hoping Uber fails - they're just saying that a company eventually needs to make money, and they don't see a path forward for Uber to do that.
A bank wouldn't keep lending to a borrower that could never pay them back; at some point - without a fundamental change in economics - this situation will happen to Uber.