It's just not necessary at all except on a few models like this with very long noses. An A320, for example, would not benefit from this whatsoever. We can't even see the nose if we try.

The concept of it, though, is the same as it is for car hoods or even baseball players wearing eye black. Black absorbs light; you can't make a paint any other color that absorbs light as well as black does. Doesn't matter if it's matte or even totally flat. White reflects light; that's why it looks white. Black reflects nothing, which is why it looks black. It's just physics.

So that's why they did it in the first place. Why they stopped I'm sure is a mix of it not really being that big of an issue even in planes like the 747 combined with simple branding and aesthetics. Airlines are businesses and even if it means the pilots need to deal with a very slight amount of added glare, they're not going to mess up their livery with a big black splotch on the nose.

FWIW, most airlines never did this to begin with. The example above is probably the most extreme you're going to find. TWA is the only US airline I know of that did it; AA seems to have mocked some up with the black brow but I can't find an actual example of one they painted that way. Pan Am's 747's were always just white up front, as were Northwest's.