Uber is fighting legal cases all over the world and in so many jurisdictions. That all costs a lot of money for lawyers and management time which could other wise be more gainfully applied.
The Uber business model is easily copied, e.g. Lyft, so they are subsidizing drivers to keep them from defecting.
The biggest secret is that managements (and Uber is not alone on this) don't really care about costs, it is only investors' money.