hmmm.. I remember in my childhood, it was the werewolf series 'Howling' that was the talk of the town. we lived in the country, farms all around us. One of my chores was to feed the dogs out behind the house before bed. It was near dark, I was about 8 yrs old and a tomboy, so I was carrying the bucket of feed to the dogs. I heard a growl from the edge of the woods, I hushed the dogs thinking it was one of them. Continuing with the feeding, I walked to the last of the dogs, which was closer to the tree line, and heard the growl again. The hairs on the back of my neck stood up, my heart was pounding, and as I peered into the tree line (why didn't I run right away) I saw a shadow of a pretty big animal with many sharp teeth. I started to back away slowly, keeping my eyes to the woods and the shadow. It moved with me. I yelled for my sisters and kept walking backward. Being far enough from the woods in my opinion I turned and ran. Getting into the house, panting and babbling about the animal shadow I saw and the growling, I was informed that one or two wolves had been spotted around the area. Yikes!
As for vampires being closely related to humans, it is said that most of the predators appeal to their prey. It is a way for them to attract, extract, and/or subdue their victim/prey!
As for how an author writes vampires or any other mythological creature, my opinion is, it is up to the creative license of the author. We all have the choice to buy or not!