Taboo words serve a function. They let you communicate something in a way would be costly if overheard in public, thus you can use them as expensive signals, so

Taboo words serve a function. They let you communicate something in a way would be costly if overheard in public, thus you can use them as expensive signals, so they make great emotional intensifiers: you only use them if you really mean it. If we were freer with these words, they would be less taboo, thus less costly, and thus less useful. Eventually a new set of taboo words would arise.