This is really concerning to me because--and I'm fairly certain I've written about this in earlier posts--strong female characters (aka positive role-models for preteen and teen girls) drew me into SFF. But these books weren't written solely by women, nor were they primarily for girls, but for an audience at large.
With parents and kids reinforcing that some topics are "for girls" and some topics "for boys" we reinforce gender norms that aren't so realistic. I thought the 60's through 80's taught us that. I want to progress towards developing believable male characters and female characters and a plot line that does not cater to one gender over another.
See, my fear is that if kids grow up reading gendered fiction that they will expect the same things from adult-level literature. That not only closes plenty of doors for girls on books with powerful, fictional role-models, but on whole topics that should not be divvied up as "masculine" or "feminine."
I don't even want to speculate as to the societal ramifications of these ideas existing in a modern context...