Humans, throughout history, have feared the dark. Our eyes are not well-adapted to seeing in low light levels and we fear what we cannot see. Our hearing is not as acute as our feline and canine companions. Nor can our sense of smell inform us what may be stalking us in the night.
Almost all of our literature, night means danger. The things that happen in the dark are twice as frightening because they happen in the dark.
Yet, in the normal course of things, pretty much what is “out there” in the dark is the same as what is there during the day. Those frigtening things are not inherently scarier or more dangerous than anything that happens in daylight. But at night, we are unsure what things are. We have to go by touch, small, and memory. It produces uncertainly which for humans is usually frightening.
Would anyone like to take guess why? Does it go back to caves and lurking saber-toothed tigers? Or is in buried deep in our DNA?