At the time when vampires came into vogue, in the nineteenth century, puritanical social standards especially repressed such issues as physicality and carnality. The vampire provided a means of expression that was safe. After all, people weren't committing such horrible acts as bloodsucking, the mythical vampires were. In this way, gender roles and sexuality were explored in quite a bit of depth. Like Sandy Stone's transsexual engorger of subjectives, Craft's Dracula, who exists to dissolve 'opposites and contrasts', is more shadow than substance.
Vampires exist where people fear to go, in the depths all that which culture shuns.