Well we need to distinguish between debt raised to lend out to customers vs equity financing.

Right, it seems like the terms on a series like that for a loan company would have terms much more like buying the debt they're going to issue to their customers than buying stock in the company.

Series E? Haven't you pretty much failed as a company if you have to go back to the water fountain that many times?

Your common stockholder (a.k.a employees) certainly have. Series E investors tend to ask be at the front of the pack if/when there is any down valuation.

Not necessarily. Funding can be used by profitable companies to speed growth or invest in moonshot experiments as well as make up for lack of revenue. And if you don't need it, the money is cheaper; sometimes, if you're offered good terms, it can be hard to turn down having that much cash on hand.