Alright, I'm gonna throw the intellectual ball around at this one, because I think the exact same thing.
If anyone here has ever read a Greek play, than they'd notice one constant in all of them: if anyone dies, they die offstage. It's better that way because it leaves more to your imagination and you have a more shocked feeling because it comes from your personal perception of how the person died. Anyone who has ever seen the original Texas Chainsaw Massacre knows this is true, because you don't really see anyone die, you just see A and C, but no B (such as the chick getting the hook up her ass. You don't see the hook going up her ass, but it's implied).
The same goes for nudity. Leaving that bit to your imagination makes it all the more tantalizing as you get to sculpt how perfect it is to you. Your imagination is one sexy tool. That and maybe certain fabrics/colors bring out a sexual response from certain people.