Devil’s advocate: they’re more demanding because, unlike employees, they are not pushovers. They have skin in the game. You seem to have equated “more likely to terminate with critical comments” to “worst.” Seems pretty reductive.
They might be entitled people or sociopaths.
Those that survive are often the result of an owner who had their hand on the wheel through some very desperate times, times which would have killed the business had they stopped micromanaging.