Horror movies, for those brave enough to venture into the genre, creates a shared experience with its consumers based on fears. While wildly individualistic, most humans share similar fears. These may range from heights, snakes, small spaces, and more existentially death and the afterlife (or lack thereof, depending on your world view).
One of the reasons I adore horror is because it’s binding. It creates a tether from one person to the next. We can come from different backgrounds and life experiences, but scream in unison at the same scary scene or the same dark thought.
To share a horror story is to share humanity.