It may go back to a society that was more religious than the world is now. In the Bible you are not supposed to spill your seed on the ground. In modern days it is a little more information than most people want. I think it's similar to a black person that says "I'm black" , or a gay person who declares "I',m gay". Sitting around the lunch table and listening to someone announcing that they masterbated the evening before just isn't something I want to hear. In other words, I really don't care, so keep it to yoursef.