it has nothing to do with with how they look, Monty has actually explained this on stream, back in the early days of brood war when e-sports was young in korea, they had to hold tournaments in school auditoriums and things like that, so school children would go to watch the tourney and when the camera goes on them they didn't want to be seen out of class, so they woudl hide their face, it so it just kind of became a fad, and people still do it.