I'd say two things, which are related:
1) Profanity itself is a form of crude honestly - in any remotely genteel social setting - 'profanity' is usually politically costly. Would you swear in an interview? No.
Ok - there are some times when 'people in power' can swear as a form of strength/power projection - but that aside ...
People who 'control' their behaviour mostly to 'be polite' - will use that communication control to gain political favour in every little social interaction. Some do it aggressively.
We all know this kind of person.
So - the 'swearers' are just using less 'filter', and so 'what you see' is really more likely their actual thoughts - 'no filter applied'.
2) If you step outside of professional circles and hang out with 'working class types' (I don't mean to be crude with generalizations) - like guys on a construction crew - you'll find that these people swear sometimes. I'm originally from a small town, a lot of working class types there - and if there are only guys around, you'll hear some cussing. These people generally don't have 'learned filters' that most professionals would use to communicate - because there is no reason why they should have developed those filters. They're just 'honest' by nature.
I've always kind of felt this way.
'Smooth communicators' are the one's you have to worry about :)