I finally figured it out.

I will recall to your memory our age-old question of why people always think about sex and how baffling it is that it pervades every form of media, communication and thought. I mean, why don't people think about ice cream that much? Why can you expect every joke that someone snickers at (is sniggers a word. i tried to type it, but spellcheck replaced it with snickers, which reminds me of the candy bar, which gets me thinking that that is a really weird name for a candy bar) to be about sex? My Very Short Introduction to History book by John H. Arnold finally shed some light on the matter.

First of all, as a basis, in this short little book one of the main points made is that a historian, or anyone for that matter, can never perfectly capture history because it is impossible for someone in the present to understand all the subtle nuances of the past and even then, each individual has unique experiences which makes it hard to piece individual accounts into a cohesive snapshot of "history" in that moment/year/decade, etc.... Point is: the human experience is really diverse. So what do we have in common? Three main things:

1) Birth. We were all born

2) Death. We all die

3) Sex. We are all products of sex and most of us will have sex in our lifetime.

So that's why it pervades everything! It is one of the few things that everyone knows about. People from all cultures know about it. People from different social classes all know about it. Jocks on the football team and Dungeon and Dragon geeks all know about it. And universally it gets most people pretty excited, so it has a strong emotive factor.

Finally. One baffling question of life answered. Now that I look back, I wonder why it was so puzzling.