Well, yeah vampires have always been the repositorys of everything that "polite society" tries to push to the sidelines: lust, rage, hunger. Everything about them is inherently sexual, they only come out at night, they usually go for the neck, wrists and thighs, they're always intensely beautiful, dreamlike creatures. But they're just not scary anymore. The evil is gone and now they're either promiscuous bisexual fops (see Anne Rice's vampire books) or tortured souls, in a constant melancholic stupor, always bemoaning their eternal life and how they are doomed to loneliness or some shit as they date nubile young women (Twilight but also the Buffy/Angel relationship), being careful to never actually give in to temptation and make it anything more than a saccharine soaked melodrama. They also create a window for the "perfect guy". We've all been ripping on the Edward character for ages (because it's easy and fun) but consider that this is a dude who will always come through for you, will never hurt you or allow you to come to harm, doesn't look at another woman and totally wants to fuck you in ways that are probably illegal in certain states but he will totally never put any pressure on the girl because he doesn't want her to be cursed or something similar. This leaves it open for the female to be the active sexual agent, something obviously frowned upon in American society at the very least, and be constantly hounding him for sexy-times, advances which he, of course, rebuffs to protect the stupid, vapid and devoid of character girl. Next to that, it is probably pretty easy to overlook that he is overprotective, possessive, murderous and fiercely territorial.
Girl: Oh you're so brooding and melancholy/sparkly! Take me now!
Vampire Boy: No, I must not! For in doing so I would lose control and kill you or turn you into a vampire like me and stuff. It would be bad, trust me.
Girl: But I'm totally hot and shit. Seriously, would you look at these breasts? Totally hot. Let's bone.
Vampire Boy: No seriously we can't.
Girl: But why? I'm so hot!
Vampire Boy: I just told you. So no. Now I have to go be creepy and sad. Then later I'll watch you sleep and not tell you about it, then cut the brakes on your car for lending that guy your protractor in maths class.