I never understand women feeling uncomfortable about young boys in the Ladies Restrooms. Womens Restrooms have cubicles, it's not like anyone can see anything. This is very different to mens rooms.
But its not just grown women using the restroom, there are the girls in there that need to be considered. And yes there are cubicles, but we all know they are not completely sealed off, there is an area where one could peek in if one was so inclined. Personally, I wouldn't care if some 9 year old boy was trying to catch a glimpse (and yes 9 year olds are old enough to want to) but my 15 year old dd would be mortified.
Also, it isn't just about seeing things, there are things to hear (obvious bathroom sounds, wrappers being opened, etc) that a young girl may not be comfortable with a boy around her age hearing her do.
I can totally understand some women of any age not being comfortable with that, and since the bathroom is meant for women, their needs/wants should come before a scared parent of a male. Those mom's and their dses have other options, those girls don't.