its actually hard for many Gpu to rendor a true black and even then your system monitor needs to be set correct to show it
This is clearly not the reason, since my gpu is very weak, but i still play just fine with jet black skin mod.
And it is indeed right that such option were available without mods. I wonder, if any developer reading it might comment on reason of removal?
Btw, Dragonborn still has such option and has zero issues with it, you can see screenshot of my character in appropriate post - i used no mods to create dragomborn, black is available for them by default.
It's really a weird desision and i am interesting about what's behind it.