Vamping out

I remember the Angel/Buffy thing like it was yesterday, I was a major fan omg, they will always be the first and most important vamp/human couple in my book, the rest of them just copying but I gotta admit I'm down with the Twilight Saga and The Vampire Diaries (although that dude is not cute at all). Anyway where does this attraction come from? Is it the cliché bad boy thing, the mystery, the darkness, or maybe just the "I would kill for you (and they really actually kill for you)" thing?