Why do people swear as punctuation?

Everyone who swears, I suppose, swears more than is necessary. And by definition people use profanity when it is not appropriate.

But there are situations in which profanity makes sense. When you drop something on your toe, for instance, or miss the train. It would be more picturesque and polite to say something like "great googly-moogly" instead of one of our quaint four letter words, but perhaps also less human.

To scatter oaths randomly throughout a sentence, however, makes no sense. It robs the words themselves of the force they might have in a more reasonable context, and adds nothing to the sentence. Eventually, the expressions no longer indicate emphasis, so they become meaningless sounds.

Also, it's coarse. Which is enough, really.