I have an active imagination. Take it or leave it.
Theory: Vampire stories are fictionalized accounts meant to be a warning about elites and central bank scams. What do I mean? Free speech was the exception, not the rule. Especially the further back into the past. Were things like vampire stories were a way to bypass the sensors but explain how society works? Figuratively, and in extreme cases literally (scarifies, adrenochrome etc) Even the ancient Greeks understood youth could be bottled up to an extent. They would collect the oily/sweat of athletes and reapply it to their own skin (hormones). Just a thought.