I think the prominence of consumption industries like entertainment, media and social media have hooked us on the idea of happiness/meaning as perpetual bliss. I suspect these industries learned it from advertising, an industry which they created and evolved. The schools and religious organizations have tried to follow suit, with only mixed success.

"Fun" is a very poor imitation of "zen" or "peace" (the Christian concept) or "enlightenment" (the Buddhist concept), but has become sort of the sine qua non of secular Western democratic capitalist societies.