Why Do People Swear & Curse?

It is not uncommon these days to find young people using the four letter words .I noticed this on Facebook most of the time. They use the words as if it the norm  and punctuate every sentences with it. What I can't understand is why do they do it? Is it due to peer pressure  or just to gain acceptance?  Lately I noticed some models even use those words as well, and on facebook too.? Don't they care for their reputation at all?  I know they are upset, but surely there are nicer ways to saying it, without using those words.  If guys use them I can understand ,but for girls to use them I still can't get use to it.In fact I get very uncomfortable whenever I hear them.There was this girl I know and I saw both her kid sisters  using them. I wanted to be a busy body and asked her why she did nothing to stop them and before I knew it she herself was doing it.
 I am not saying it is alright for guys to use it, but rather surprise to find girls using them as well.There is quite an interesting article on swearing here. and another one here.