I don't understand how you can look at these costumes and think they would be improved in any way by the guys painting their skin black.
The people who claim buh buh buh accuracy are fools.
Good examples.
Sometimes being black is an identifying characteristic for a character, if not the defining characteristic in some cases, so I certainly understand why some might think to incorporate that into their 'costume'. Where a white character might get a cape or something, a black character can often be 'the black character'.
I'm not taking up the '"buh buh buh accuracy" argument, but I can see how someone ignorant or uncaring about the social implications of black face might incorporate that into a costume for the sake of accuracy, seperate from any racist notions.