Although "pitch black" isn't exactly realistic either, most of the times.
It makes sense in inside areas, a forest at night or moonless, overcast nights, but nights with moonlight can get relatively bright in reality (of course even during full moon they are usually still darker than what we get in the average AAA).
If a game has (gameplay-affecting) dark nights, I expect it to give me tools to deal with them, integration into the game and a good lighting system on top. This made nights in Stalker so cool. Dynamic lighting and a somewhat useful flashlight not only help a lot with atmosphere, it also makes for more interesting gameplay.
On the other hand the big problem with darker night mods in e.g. Bethesda games is the bad lighting system used by those games - many times making nights darker also means making your lightsources darker, putting you into darkness with only a 0.5 meter dim glow acting as your light source*. Of course that's not fun, that's just tedium - nights don't become something dangerous, but which you can deal with given the right tools, but something you want to avoid simply because gameplay becomes shit (in before "And where is that different from broad daylight?"
).
That's why I prefer darkness in such games to be darker than vanilla levels, but not so dark to become pitch-black.
It was never meant to be more than cosmetics, so I would rather keep it that way (only better looking) than trying to transform it into something it can't be.
* of course you can e.g. mod it further to provide for better lightsources or other ways of dealing with the darkness.