Playing roller-derby

Roller-derby is traditionally a girl´s sport, it´s the way it works everywhere. (Or it's like that everywhere.)
But in Spain it seems it will be different. We know that because roller-derby girls are doing making an incredible effort to promote this sport in Spain, and the tracks (the places for training and playing) are given to boys who want to play roller-derby.
Why? We don´t know. May be Maybe the answer is because the world continues in the hands of men.