I think that this works the same in most forms of media. The world is a twisted place. Parents will much more likely let a child watch acts of ridiculous violence than let them see sex in any form. Trying to look for a reason for this is hard, but thinking at a cultural level, I'd say that tradition plays a huge role.
In Rome, which was the biggest empire of its time, had violent gladiator shows at colosseums but I don't remember hearing of people making out for an audience or something like that. I'd say that Roman culture had a pretty large influence on modern day culture, it being the widest spread civilization back then. EDIT: Sorry, apparently there was a lot of sex going on. But I'd still say that the violence is what they are remembered more for.
The same goes for the bible: lots of people die, very little people make love. And the bible is pretty much the most influential book ever.
Besides, in a situation of conflict, isn't it better for a nation to have its inhabitants be ready to kill for their country rather to just make love with the enemy? This may be moving to the crazy conspiracy department, but I'd say that governments want us to enjoy violence, so that we can tollerate or even support war more openly and keep us from loving and being hippies by censoring all the other shit.
