The common every day curse word has been rejected from polite society since before William the Bastard became William the Conquorer. (and really long before that)Most of the English swear words are based on old French and old English. The reason they have been rejected from society for such a long time is that men thought that women needed to be protected from the harsh realities of life. Women, then took it upon themselves to reform the language and remove the coarse terms from their hearing at all costs... The Victorians were masters at reproving coarse speach in front of the ladies, yet using it when in the presence of lower caste females... Then you have the influence of the church and the Bible stating that such terms are unnecessary, and should not be used, since one can get their point across without swearing.

A slightly different slant to the previous answer by atreadia, giving a European perspective - I would say that the most powerful influence in the restriction of curse words is the church. I am not aware of any real restriction of 'curse words' in anglo-saxon or viking society in the pre-christian era. As so many of these words are a corruption of a word or words which the church has deemed blasphemous, and therefore improper, they become taboo. Also, many are words which are associated with intimate parts of the body or acts of the body which at various times in the last 1500 years the church has tried hard to ignore, or has associated with the idea of sin. For centuries the church has worked in Europe hand in hand with all kinds of administrations, and has a long standing involvement in social control. It should be said the church usually had at least some interest in the soul of the individual, and advice against swearing would be part of this, so little criticism there. Socially, what changes in the last say 300 years is the emergence of a larger middle class out of a working class or agricultural base. These are people who 'raised themselves' in society, and would be expected to display outward signs of this change in order to 'fit in'. Inevitably, if you are suddenly in the position of moving up the society ladder, you don't want to make a fool of yourself at dinner if you say something unguarded, so speech has another reason to be carefully watched and controlled. Victorian society even avoided perfectly 'non-sweary' words, and for example would refer to things like 'masturbation' as 'solitary vices'. They also put skirts on their table legs so no-one would have lustful thoughts (presumably this would also be to protect the virtue of any easily-led chairs?). To give the flip side of this highly prurient coin, at the same time this was happening a street in the East End of London was given the name (I don't know if I'll get away with this) 'Grope-C**t Lane' by locals as it was so widely used for prostitution. So the various levels in society, with a little guidance from the church, form their own version of what is acceptable and it's still with us - I know many who dislike certain words or never use some of them, but none who avoid swearing altogether. I grew up in a time when it was unheard of to hear violent swear words on television or radio, and almost as hard to hear in the realm of film. In real life, I don't think I heard anyone swear until I was about 8. 'Lady Chatterly' and all the court nonsence happened in the 60's. It's not that long ago, and things are changing (many say for the worst) but I think it will be a habit that's slow to die.