Where I'm from it's a marker of lower intelligence. It demonstrates that you lack the vocabulary to clarify how you feel so instead you use the same words kids use. ITS GOT WHAT PLANTS CRAVE!!!
The accusation, that my extensive use of profanity, implies a lack of mental faculties, to the point of concluding that I'm some kind of imbecile, is incomprehensibly erroneous.
I'd say its actually a marker of coming from a blue collar worker background over anything else. I get people from the dumbest labourer to ever pick up a hammer to project engineers and automation programmers and we all swear as punctuation pretty similarly. You can tell when someone's a corporate narc because they just can't swear right. Brains wired wrong for it. Now I don't swear a ton when I write because it just doesn't feel as natural compared to spoken word.
I think a lot people who swear all the time sound dumber when they're places they aren't supposed to swear because they have to constantly run over and censor everything they're trying they say on the fly and as Ricky from Trailer Park Boys would say "If I can't smoke and swear, I'm fucked"