I'm a bit surprised by this request to be honest.
Night time is part of the universe, to make it as realistic as possible they worked out the planets and the sun, eventually when the possibility was there, day and night cycle as it should be.
At first, the night was really dark, how it's supposed to be, because there are no lights in the wilderness, just in towns. The moonlight was the only thing that made night a little less dark, being able to see.
After a while people started complaining that the night was way too dark and after some consideration MA noticed that only people with high end monitors were able to see in this darkness and decided to make the moonlight at least 3-4x as bright as before. Making night visible to people with mediocre monitors.
The reason they did this was because they can NOT remove the day/night cycle, adding the option requested here is not possible. Why? Well, if someone can turn off the night and is competing in an event against someone that has enabled night. The one using daytime only will have a huge advantage over the one playing nighttime.
To compete, everyone will disable night and in the end nobody will have a cycle at all because they are FORCED to disable it due to problems like these. This is not something the players want, nor MA.
What is the real problem here?
The problem is that (I think) there is a small percentage of players that run old monitors and/or budget monitors that do not have the capability to show the actual image. This often shows in things you mention, dark scenes where you can't see anything, but it is there....
I've posted in threads about people complaining about not being able to play on Windows XP too. Please upgrade your hardware, I'm not saying you should spend a fortune on new stuff. But do you really expect to play a (graphics wise) up to date game with hardware technology from 6+ years ago?
It's not going to happen.
Now you may ask if I have the newest hardware? No, I just buy quality. My monitor is ~4 years old and I can see EVERYTHING, even in the black night it used to be at the introduction of the day/night cycles. And yes, that is in windowed mode.