Even in books it happens. In The Dark by Richard Laymon is a good example of this, though I'm also told it's a staple of books in the pulp-fiction realm. Honestly, I got so tired of hearing about the protagonist getting poked in the boobs, or her panties getting soaked with sweat. Gratuitous, that's all it was.
Still, why is this?
Well, that I know of, there's two main reasons for this.
Huh? I know, but it's a fact, especially of most of the Horror that came out in the 80's and early 90's, as well as a lot of the newer Horror that now pays homage to those days.
See, here's the thing. The couples that have sex, and the girls that are bouncing all over the place. They die. It's the conservatively-dressed, virgin heroine that lives and finds a way to escape or stop the killer. The moral of the story is that sex is bad. It's a risky behavior that, if you engage in, will get you killed.
Now, to be fair, society has become more accepting of sex (Seriously! Don't laugh!). And this has become less and less of an issue. It does still pop up though, and the moral of the story is that sex is a sin, and being a sinner gets you killed.
2. Sex sells.
Yeah, we know. Slap a pair of boobs on the screen and suddenly all eyes are glued to the TV. (Unless you're not interested in boobs.) Trying to sell a soft drink? Have a beautiful pair of lips on a straw.
|Pictured: Selma Hayek's boobs. Also, George Clooney.|
This is actually the kind of sex you get in a lot of the classic pulp fiction novels like the aforementioned In The Dark. It's filler, designed to titillate, hoping you'll keep reading just to get a little bit deeper (ah-hem.) into the story.
Now, there are movies that use sex sparingly, and appropriately for the story they want to tell. The Last House on the Left, starts with a horrific rape scene, which leads into the rest of the movie. The rest of the movie would never happen if that one event hadn't occurred.
The other movie that springs to mind is, rather obviously, the Horror-comedy Teeth. I'll just leave you with the poster of that one, and that should tell you all you need to know.