This questions goes side by side with why the E.R. is swamped with people that perhaps could have been or should have been seen during the day in a doctors office. As night falls, there is a sense of aloneness that comes to us that creates anxieties not felt in the daylight hours. We often find ourselves feeling as if we have been cut off from the world and our minds begin to wander. It is fact that we fear things in the night that do not cause us any issues when we can see everything around us. The world is awake and moving and the fear of not being able to reach someone because of the night time isn't a factor.
When night time comes to us, we also face quieter times. The family and those we know and speak to in the day are sleeping soundly. With the silence comes idle time that allows our thoughts and imaginations to run free. We think deeper and because our minds are not filled with the business that we have during day light hours, we tend to think about things we did not have time to ponder while the rest of the world was awake.
Night-time, from the time we are tiny tots, is a scarey time because we feel alone. As we grow, we learn to control some of those emotions but even as adults, darkness brings with it an insecurity that effects everyone from time to time. Things not seen, whether they are real or simply our over active minds teasing us, are still fearful for us, even as adults. Darkness has been used as a torture for thousands of years because the mind goes to places in the dark that it does not as long as we can see what is around us.