No matter what kind of person you are, there is always a thirst for knowledge of the unknown. You can be as fearless as one can believe, you still want to know what's making soft creepy noises while you are home alone. While it may just be the air conditioner, a list of possible suspects run through the brain; a ghost, a vampire, or even a murderer. It's almost like the brain's way of being entertained.
The occult is present in many American movies, books, or TV shows. Some ranging from sparkly vampires, to illuminati conspiracies. It creates a magnificent source of entertainment because the unknown is known to be pretty awesome.
Humans have also had a long history to fill in the unknown with ideas of their own. Back in the early days of Puritan America, any sightings of unexplainable phenomena was blamed on witchcraft. This happens even in the present. Like the wonderfully realistic show Ghost Hunters, any unexplained phenomena can be thought to be the work of a ghostly presence.