It plays on our common fears. Fears of the unknown, of being alone, of the dark. A 'two sentemce horror story' like 'I was home alone. The lights started flickering and I couldn't find the switch' taps into those basic fears and makes us shudder because we can easily imagine ourselves in that situation.
Here is one. 'The old house was silent. I heard a child's laughter, but I was alone.' This simple two - sentence horror story creates an immediate sense of unease. The contrast between the expected silence in an old house and the sudden, unexplained sound of a child's laughter when no one else should be there is quite chilling. It plays on our natural fear of the unknown and the unexpected in spooky, deserted places.