Vampires don't suck; they scrape and lick.

You ever think a vampire seduced their prey, did the whole cuddle-lean thing like in the films, then got ready to dig in only to realise that the victim's neck hygiene is awful? Got that thin gunky layer of filth that gets stuck under the nails easily? That must be the perfect anti-vampire tool, maybe it's a natural part of evolution in defence against monsters? I mean imagine trying to give that neck a hickey, only to get it all over your lips and tongue. Blegh, that'd ruin the mood.