I think the problem comes when you walk. Lets assume you have properly fitted pants that either hit or break at the top of your shoes (I don't want to argue which is better). In that case, when you stand up, your socks are covered and you see all black from the waist down. But now start walking, the knee bend raises the pants, exposing your socks. If you have black socks, then all you see is black from the waist down. But what if you wear white socks? Then while walking, for half the time you don't see your sock, and half of the time you do see the sock on each leg. So while looking at a leg you see black/white/black/white/black/white/etc. It is like those annoying flash ads on some websites. The point of getting dressed up with black pants and shoes is too look good - not to look like a stupid flashing advertisement.
That said, I don't care if people wear white socks with black shoes and pants.