It is hard to know why people obsess  on certain things. During the Middle Ages, one fate in the next world was the major issue. And since the right doctrine determined that fate, nations would go to war for that. In the Victorian Age in England , death was the major issue. One tomb or grave stone was just one aspect of this. Mainly people were obsessive about their legacy. But sex could not even be mentioned. Nowadays all that seems ridiculous. Nowadays people obsess about sex and bring it up all the time, --it is on the news constantly. But ones' legacy on the news? Or one's fate in the next world? You will not hear these issues on the news. And besides sex, there is race.  

Why do people obsess about it? Who knows?