Thing is, the US military increasingly works at night due to advances in night-fighting technology. Unfortunately, our enemies know about this too and non-US nightvision tech has caught up if not surpassed US issue NVGs in many cases (see the latest in digital NVGs.) You have but to watch footage out of Syria to see Russians using their NVGs and seeing that theyre for all practical purposes just as good as ours. And they will sell their top stuff to the world market unlike us.
However, there is no reason a camo pattern cant serve both day and night service needs. Several other countries and companies have produced patterns that work just fine for both. They dont incorporate much if any black, though. Darker grays and such, yes, but not actual black.
Then we have thermal sights to deal with..