Are Uber drivers employees of Uber? Or are they contracted out, or independent, etc? If they aren't considered employees, then the $1B gross would not really be gross revenues under GAAP.
Those employees are also often contractors of those companies...
Think about a site like Expedia, or Orbitz. They do not claim the entire price of the ticket as their revenue, since that money is going directly to the airlines. Their only revenue is the $10 they make from a ticket purchase.
This is the same issue that Groupon ran into pre-IPO where they were claiming the entire deal as their revenue.
I'm just speculating, of course, but if the title is to be believed, it supports what you're saying, I think.