I believe it's important as a means of emphasising your true feelings about a topic. I guess it's important in the same sense that shouting to show anger or speaking softly to show sympathy/empathy etc. is. It's just a lingual way of doing it rather than a tonal way.

I do think however that swearing for the sake of it is uncalled for - the people that swear after almost every word when it adds nothing extra to what they're saying actually annoy me.