I would guess it's because we cannot see in the dark, thus we do not know what is there.
Survival instincts; being afraid of the unknown; darkness meaning "evil", there's all sorts of reasons. But I think people are actually scared of what's in the dark, rather than the dark itself.
Well, I'm not more afraid of it, so I can't really say.
People are afraid of that which we canâ€™t control, donâ€™t know, canâ€™t see. You feel helpless, because you canâ€™t fight what isnâ€™t there, or what you do not know. The dark also gives you time to think, and it often forces you to face fears, or things that you refused to think about previously. You canâ€™t hide in the dark, not from yourself. There is nowhere to run, no way to hide. Quite simply put, humans are afraid of what hides in the dark. Sometimes that is a predator, sometimes, that
it's because most people are not used to the dark. We're more used to the light. Imagine being totally blind from birth. You would've grown acquainted with darkness, having never known what light is; and you would not fear darkness..it would be your old friend :)
Its because humans are programed to be afraid of the unknown when theres nothing pointing towards the result being good. Most humans rely on eyesight to let them know things are safe but when you can't see more than a small amount your brain instinctively goes on edge trying to boost your other senses so that you could have a better chance of protecting yourself. The boosted senses are what freak you out. But when its light its no problem.
So in the way you just also explain why people may be afraid of the future and of change. When we make changes to our life's we wont know what will happen. Same as the future. We wont know what the future will bring. We cant see what change will bring just like we cant see what the future holds for us.
I think it's probably because we can't see as well in the dark, so there's more room for our imaginations to come up with things that could be out there. A lot of people are afraid of the unknown, but it may also be a survival instinct. If you don't know what it is, stay away from it because it could be dangerous. That type of thing. Interesting question :) This is just my take on it.