The horror genre requires immediacy. Coming face-to-face with the shock of the unknown. Former models of behavior or thought upended.

Because if you extrapolate out beyond that initial encounter with the horrifying, you approach the mundane, because people can get used to anything. And then it's comedy.

Your first vampire attack-- when you don't even know what vampires are-- is horrifying. What is on you, what is it doing? Why am I weak? How does this end?

But someone hitching a thumb at a castle and saying "That place? Totally full of vampires."

Now they're a known quantity. Which is hilarious.