Anybody familiar with George Carlin at all? As a stand up comedian, he was an extremely intelligent man, with much knowledge of the English language, among other things. Yet he swore constantly.
So no, I don’t think people who swear a lot indicate a lack of vocabulary. Sure, Carlin wrote all his stuff in advance, but I really don’t think an excessive use of the word fuck, shit or whatever else that’s considered a swear means a lack of vocabulary.
The problem with swearing is that it’s so common that it has infiltrated the languages to a level that reaches the norms of everyday talk, (at least English and French as far as I can tell) and when it’s used in emotional response, it’s just what comes out for a lot of people…what, am I supposed to be all educated and imaginative when I stub my toe or when I drop and break a plate? If this myth of swearing was true, the same could be said of people who don’t swear, but still use common words or expressions constantly; oh my god, right on, awesome…swearing is offending so it sticks out, and therefore it’s easy to condemn, but I don’t think it should be taken away and imprisoned on its own, away from other, non offending words and expressions used by people all the time. I bet a lot of people who don’t swear or really dislike it would argue my point about non offending words used daily, within the same situations as swearing.
The only time I would cut swearing away from the rest is because of its rebellious nature and how many wish to use swearing for that very reason.
I’m pretty sure most people are a slave to their culture’s phrasal habits, or out of nowhere wording that occurs once stuff like fear, surprise or anger or whatever present themselves. That doesn’t stop those very people of being intelligent or imaginative though.
I swear because that’s my style, and I’m far from being a genius, but I’m very capable of taking the swearing away and replacing it with something else if I have to, whether online or in real life. Although I do have a big interest in the history of cuss words and expressions, that kind of helps me. Sure, some overuse it, I may be one of them, but I’m really not convinced that everyone who swears lacks a proper vocabulary/education/whatever else. There have been plenty of people in my life who swore/swear all the time, but have shown proof of varied vocabulary.
I think the main issue is how prominent it is in a lot of languages, and some might do it without thinking, or they don’t care who they offend or whatever. But that doesn’t stop that person from being able to vary and color their vocabulary with something else, if they want to.
My point however, is that more accepted words or expressions, as far as I can see, have absolutely no difference with constant swearing when it comes to this issue of vocabulary, other than swearing being offensive to many.