By being in the right place and right time once, making it impossible for users to leave, and buying up all their competition before they become a serious threat.
Also, they typically started with much more of a high quality culture when they were small and people's contributions were legible.
Once it turns into a giant bureaucracy with people you've never met judging a promo packet by rubrics, while they're unfamiliar with your whole org.. the incentives get diffierent.