The point is that I raise my daughter and my sons with the same expectations. Maybe I am a more relaxed father than most.
But I am curious... You really never overheard your kids swearing?
My oldest son was an athlete (boxing and soccer). Around these kids you would hear swearing.... not directed at adults, but you would hear it. My daughter's friends like D&D and Anime. It is the same thing ... It is part of the social ritual.
My daughter hosts D&D games at our house, and I drive to Anime conventions... They are always respectful to me, but I hear it.
I have always made the distinction between swearing to hurt someone, and swearing to express emotion or belonging. I don't mind "this game is ******* cool" so much. If someone says "you suck asshole" then we have a problem.