The unknown aspect. In a true scary story, when there are things that can't be easily explained, it terrifies people. For example, in a haunted house story, if there are strange noises at night and no clear source, it plays on our fear of the unknown.
One true scary story is about the Bell Witch. In Tennessee, the Bell family was haunted by a witch - like entity. It would whisper threats, move objects, and torment the family. For example, it would pull the hair of the family members and slap them. Strange noises filled their home day and night, and they were in constant fear.
One true scary story is about the Bell Witch. In Tennessee, the Bell family was haunted by a malevolent entity. It would whisper threats, pull hair, and slap family members. The apparition was said to be the spirit of a neighbor woman who had a feud with John Bell. Strange noises filled their house at night, and it was a terrifying experience for the entire family.
The unknown factor. In true scary stories, we often don't fully understand what is causing the fear. For example, in a haunted house story, not knowing whether it's a ghost, a demon, or some other unexplained entity is terrifying.
It's hard to say. You'd have to look into the background of the creation of 'Old People' to know for sure. Maybe the author drew from real-life experiences or it could be completely made up.