$50b in revenue last year is nothing to scoff at. They have levers for profit but instead re-invest every dollar. Your argument sounds exactly like what people said about Amazon years ago.
Why that $14 billion can not be called revenue is Uber specifically structures it's business to make sure their drivers form no part of the business, instead they insist all their drivers are independent contractors.
They do that specifically to reduce their running costs and hence maximize the profit on their actual revenue.
That would be like saying all iPhone App developers are working for Apple, when in fact all Apple does is take 30% of each and ever dollar these App developer earn in sales.
Likewise Uber just puts it's 30% Uber tax on every dollar it's drivers earn.
$50bn is total bookings, which is impressive. Revenue, I believe is $11bn runrate. But that doesn’t address cash flow depletion. I do believe they have runway though
For example Uber's last quarter revenue was $3 billion on some $14 billion in bookings, with a loss of about $800 million.