My grandparents and parents used to spout idioms like, "hard work is its own reward" as if they were inalienable truths.
IMO it's baked in at a cultural level, at this point. Where did it come from? You could point to the harsh Puritan work ethic, or the myth of meritocracy, or the rivers of blood lurking in the US' past, but there's probably no single root cause.
