They're not losing money on rides.
Uber is two things. A moderately profitable ride sharing company, and a loss-making VC-backed R&D enterprise working on things like self-driving cars. If they shut down or spin off their R&D they could continue on as a ride sharing company indefinitely -- they could probably lower prices because they're not using that money to supplement the VC money they're spending on R&D.
But you only separate the R&D if you think it won't ultimately lead anywhere. If they eventually actually get self-driving cars working then it's obviously to their advantage to be the same company that people are already using for car service.
I've never understood that. How are they subsidizing it? They take over 25% of what the customer pays and all they have to do is run the app. Whether they charge $10 or $15 for the same ride the cost to them is the same. It doesn't make sense, they don't have any extra cost by making a ride cheaper.
I hope this explains it more clearly.
https://www.vice.com/en_us/article/9a3vye/uber-true-cost-uh-...
How about using the S-1 or quarterly filings instead.
Uber also pays driver incentives beyond fares (e.g. for completing a certain number of rides).