You are incorrect in assuming there are no physical differences. The difference in average reaction time between men and women could alone justify seperate leagues. Several other differences play a role such as mens vision on average better percieves moving targets. It also depends on the game. Men have a clear advantage in shooters like cs:go but very much less so in Starcraft 2. Scarlett (a woman) is one of the best zerg players of all time regardless of gender for example. It's silly to assume that there's just so much red tape or something that women can't break through. If a remarkable talent in cs:go was a woman she would be hired by a team because they want to win. The gender seperation is a product of real differences, and also a consequence of much fewer women than men being interested in esports to begin with.