All the perfectly-successful, privately-owned companies seem to have a price at which they eventually sell out to a soulless conglomerate, q.v. StackOverflow and GitHub.
(a) Some dude is making $500K/year at Google or $250K/year elsewhere or whatever
(b) They start a privately-owned company and hit $1M/year personal income and are pretty happy, at least happy enough to not want to go back to working for someone else
(c) But then soulless conglomerate offers them $20M+ in one go for an acquisition
I don't blame them for taking the $20M. It can be a life-changing amount of money.
The owners have either (at great pain) developed a sufficient capital base and succession plan to provide continuity (which would require significant ongoing investment in R&D out of cash flow in order to develop competitive products), or they must find a plan for the business. Going public solves this problem for them, so does selling privately. Neither option really eliminates the requirement to remain competitive.