It would seem that Blizzard had a hand in this move. A Blizzard rep delivered a statement to GamesBeat about the issue, stating:
One of our goals with e-sports is to ensure that there’s a vibrant and also inclusive community around our games. We do not allow the use of our games in tournaments that do not support this, and are working with our partners to ensure they share the same goal.
Well done, Blizzard.
A women-only division still exists in order to improve the visibility of women, who are still in the minority at these events. Full integration would be better, I feel, but extra opportunities for minority groups are not a bad thing.