Testosterone has a direct, measurable effect on competitiveness and aggressiveness. Why wouldn't you think this would affect the overall sports preference between the sexes? In an environment where men have significantly higher testosterone than women, wouldn't there naturally be more men than women in an aggressive sport like football? Would you expect a 50% gender parity in such an environment?

Culture plays an effect, but we really need to realize that biology probably pays a role too, and potentially affects gender parities in many careers.