Gendered chess tournaments make a certain amount of sense. The main issues are that women are less likely to play chess due to societal and cultural factors and without their own division would have even more societal and cultural roadblocks to joining the game. This isn't touching on how getting certain titles requires winning specific events that would prove even more difficult for those same reasons.
Basically without gendered tournaments there would be even less women in chess and it would be even more of a "boys club" than it already is.