My summary of where all the money goes:

-- Every on-demand service struggles with the problem of peaky demand, variation of >50% in peak to average traffic / demand

-- Peaky demand is inherent in our consumer / passenger / people behavior, not going to change any time soon -- think of the daily hours typical for commuting, eating, etc.

-- These services make their money / entire value prop on serving peaky demand quickly, but you need labor willing to match those times, otherwise people are sitting around underutilized

-- Until you have automated cars / labor, you have a really hard time recruiting people who are happy only to be paid part-time

-- Drivers / labor have to be paid pretty much on a full time basis to keep people working for you (whether overtly or implicitly through promotions, marketing, sign up bonuses), otherwise they sign up with hopes of steady income, and then quit. ("I love being able to set my own hours", etc is the exception, not the imaginary bulk of people working for a living)

As long as these conditions prevail, this is where those companies' cash is hemorrhaging to.