https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcSW8e3GFxzuZRibvvuqFTTR71Fx1iqrC6oNE3PHwxm8lSdPlXd0 (Unsupported image host)

Black looks good, so people will wear it. In real life or otherwise. Those people don't just wear it to spar, they wear it all the time in game. I don't wear solid black, but black is certainly the main color. Try out some of the other colors, they don't look so great if you put them for every part of the body.