I have no specifics, but I can make a few guesses:
1. They are stockpiling cash to afford lengthy, costly, legal battles for their business model. Although there is a huge potential this could backfire entirely and investors will be out millions.
2. They are stockpiling cash in expectation of having to pay drivers as employees and provide benefits, etc... to those drivers.
3. I am sure there is a good amount of money earmarked for marketing/sales efforts to take on new markets.
4. I would expect that they have several "on-demand" products in the works (i.e. same day/hour delivery service) that will require upfront capital.
