Welllll.... there are hassles associated with being a public company beyond merely "people holding your feet to the fire of financials." You have to comply with Sarbanes-Oxley, which is just a real pain in the ass, for example (source: I worked for NetSuite as they went public, and coming into compliance with SarbOx was a bunch of work).

A private funding round with a limited controlled equity buyback from employees gives you a certain amount of control that going public does not, too -- a company like AirBnB that had a broadly successful IPO would presumably mint a ton of millionaires among their employees, and I would expect to see a substantial talent drain once that happened.

But yes, I assume that "financials aren't in great shape" is the majority explanation for AirBnB's failure to go public.