Why are horror films traditionally bad?

Movies are an art form, and as such often try to elicit emotional responses from us.  Why is it, then, that if I say a movie was designed to be "heartbreaking", you would have different expectations of it's level of quality than if I were to say that it was meant to be "terrifying"?  There are two easy answers to that question:  Experience, and a certain lingering Puritanism.

I'll address the former first;  Yes, there is a long history of shitty, shitty horror films.  For every Silence Of The Lambs, there are a thousand straight-to-video zombie films, each more inept than the last.  And here's the problem;  horror fans love it.  We (I'm most certainly including myself in this) eat them up, we love them so.  A true horror fan appreciates a broad spectrum of fright, from the divine to the defecated.  We savor every wooden performance, every ridiculous plot twist, and every unconvincing monster make-up.  

And so I present the first killer of quality;  the horror fan.

A balanced diet of cinema is all I'm asking for here.  Cake and soda are fine every so often, but we need to balance them out with whole grains, fruits and vegetables.  And vegetables don't have to be boring;  movies like The Shining taste great, and they give your eyes vitamins that they need.  

The reason studios keep making shitty horror movies is because we keep going to see them, even as we bitch about them!  Here's a thought;  If you, like me, are tired of the overabundance of crappy horror, put your money where your mouth is this Halloween, and check out Paranormal Activity 2 instead of Saw 3D.  I'm not saying that PA 2 will necessarily be a masterpiece, but based on the advertisements it looks like it's at least TRYING to be good, something the Saw series hasn't attempted for several years (and some would argue, ever).

The second hurdle for the reputation of horror films to overcome is more ingrained and widespread;  there's something in our culture which casts the feeling of terror as prurient, and even if we like a horror film, we often feel bad about it afterwords.  Horror films are not the kind of movie you date;  they're the kind of movie that you have great drunken sex with, and then never call again.  Until the next time you get blitzed.  

I've often found that high art is something regarded with a certain detachment.  Perhaps the genres which evoke the most uncontrollable reactions, like laughter and screaming, can't as easily be analyzed with that cool gaze.

As far back as I can remember, horror films have been relegated to the lowest rung on the genre scale, barely above pornography.   It does lend the genre a certain punk rock aura, which does give me some pride as a fan.  But I dream of a more ambitious genre.  I look at the next couple of months of releases, and we have high-end representations of genres such as fantasy (Harry Potter), science fiction (Tron: Legacy) and the western (True Grit), and I wonder;  where's my Oscar season horror film?  Who can bring this genre to a place of respectability that it has never before achieved?