It's an idea that goes back to Babylonian times, and probably far earlier. Blood has all sorts of associations and some of them are quite intense. Put the various ideas about blood - life, pain, death, childbirth, wounding, dying - together and you have something that takes on a powerful spiritual and cultural significance.
Now imagine a creature that lives on blood, with all its intense symbolism and you have something designed to scare the bejesus out of people.
the other core idea associated with vampires is that they aren't human: they may be the Babylonian Edimmu, or the Hebraic Lilim, or the much, much later eastern European Nosferatu concepts, but whatever they are, they are unnatural, being either demonic creatures of the underworld, or descendants of a demon queen/adam's first wife or indeed a suicide condemned to walk the earth.
So whatever a vampire is, its something not-human living on something with intense symbolic significance. It kind of kills the point if they also tuck into a curry on Friday nights too...
Thank, a lot for the answer. You said that there was more to the blood than symbolism. What's the rest, and what about immortality? I really shouldn't be asking these questions but I'm curious, and i pray it dossn't hurt me.
Immortality is one of those ideas that tends to be tied up in the unnatural. As mortal humans, we sort of think in terms of mortality - you are born, you grow up, you are mature, you get old, you die. Immortality, on the other hand, is outside the natural order of things.
We associate immortality with divinities - and with things which are outside the "right" way of things. The ancient (and nasty) story of Aherasus, the Wandering Jew; or the story of the Flying Dutchman; or Oscar Wilde's "Picture of Dorian Grey" - the undying is unnatural and evil.
So vampires are unnatural (not dying); unnatural (drinking blood/life to survive).
Vampires are also associated with certain strictures - rules and laws, which don't apply to the living. These things have sort of accumulated around the vampire legend, but they tend to apply to evil spirits in general: they are afraid of or harmed by running water, church bells, garlic, daylight and so on.
So if vampires are anything, they are the absolute apotheosis of the folkloric expression of evil (not to mention the other associations with rape, incest, masochism and so on and so on).
what???? wow but the wampires dont need human blood to survive according to new stories jaja anyway they can life drinkin the blood of animals so whats with the vampires they can life among us or not?