Amazing how most of the replies are being rude to the OP rather than expecting teens to have manners in public.
Isn't it just. It kind of goes to proving OP's point, with which I completely agree. But many people on MN seem curiously fond and protective of their swearing. Just because MN doesn't condescend and allows adults to express themselves, that seems to cause a lot of folk to feel that they have to swear as often as possible.
Swearing full-stop isn't a sign of limited vocabulary at all, but using it as punctuation very clearly is. Endlessly using any word/few words is. If somebody repeatedly used the word 'sausage' or 'giraffe' or 'trousers' in the same way, a dozen times in every single sentence, nobody would ever disagree with how ridiculous they sound (Tourettes or similar aside). That doesn't mean there's anything wrong or low-brow with ever using those words at all either - it's just about context.
The most tiresome of all are those who don't even know what they want to say (if anything), so will just start with a random swear word before a long pause as they then think about it. I'm not talking about responding to something significant that takes you aback, but just ordinary mundane chat. Nobody can convince me that that is not a sign of seriously stunted vocabulary.
I don't accept that we can brush it off as OK for teenagers, when they're doing it in public. Fine if they want to speak like that in private and in messages to each other, but they're old enough to understand that it's not appropriate language to subject other people to out in public.
I especially wince when people - whether teenagers or adults - swear in front of small children. MN threads on the matter usually seem to converge on 'well, they'll hear worse when they get to school, so it's fine'.
It's amazing to think that people on a parenting website not only don't seem to understand that we treat young children as the young children that they currently are and not as the older children and adults that they will eventually become; but also that it's seen as a race to the bottom, whereby those with the lowest standards should be allowed to dictate and nullify everybody else's.