why not IPO? I mean I think going public is terrifying and awful, but have to exit sometime right? if you raise at >$10B you would need to IPO at >$20B no?
Being a publicly traded company sucks. I imagine a lot of this financing will go to cash out early investors, providing liquidity for those who need it, while still keeping the company private.
It's a common strategy with tech companies. (See Square, Uber, Dropbox, Twitter, etc.) The first major instance I remember was the $300MM DST/Yuri investment in Facebook in 2009.