Because everyone uses the fucking women's.
All women, all children, all older adults who have women with them as carers (so far so good), men who want to be women, men who are dressed as women, men who don't want to go to the men's (I'm talking about you, random man at the theatre who wanted to go "with his friends"), men whose "gender" isn't manly enough, and anyone who is dressed up as a caricature of a woman on a Saturday night out 
Sorry, I'm a tad angry. I've just returned from a weekend where I queued for the loo everyfuckingwhere I went. Airport, bus station, restaurant, museum, theatre, every place I went to I stood in a queue while a dozen men whooshed in and out the door beside me.
To be fair, pretty much all of those waiting were the usual cunty type of women. But adding more to our queues and reducing those for the men's is just bloody infuriating.