Here we go again with the silly argument that accessible toilets should be vacant at all times for people who can't wait. Disabled toilets were not created for people who need to get to the toilet quickly, they were created for people who can't access normal toilets. Some places only have an accessible toilet for everyone to share.
There may be times when common sense means that a non-disabled person will quite reasonably use a disabled toilet. However, most places only have one single disabled toilet. Whilst you may say that they can queue just like everybody else has to, it's hardly fair when there's only one they can use, whilst other people can use numerous ones.
If you were at a large, busy event, where the ladies' toilets had 12 cubicles, would you be happy to have to queue with all the other women there - with the understanding that they could use any of the 12 as they became available, but you were only allowed to use the first one, all the while watching numerous people behind you in the queue using cubicles 2-12, as well as those ahead of you freely using number 1, when they could use any of the others?
Maybe unfair sex-separated toilet provision is a whole load of moaning about nothing too: perhaps it doesn't matter if a long queue of women are having to each wait 20 minutes when the men are straight in and out in half a minute.... because there are toilets suitable for women to use, so what's the fuss, eh?