My mom believes in ghosts, and demons, and angels, and just about anything else you can think of (UFOs). As a child, I also believed; and for me, it WAS scary. I appreciate the magic of Christmas, but I don't see a benefit to pretending fake scary things actually exist. I certainly would have preferred to grow up more founded in reality.
Also, when my bipolar sister began cutting herself as a teenager she told my mother that a demon cut her in her sleep. My mom believed her, and thus my sister didn't get the help she needed as early as she should have.
Part of the problem in life is being able to figure out which real scary things exist and which fake scary things don't exist.