Because diversity of female characters has been lacking in comics, film and just fiction in general, coupled with an upsurge of feminism; there seems to be this perception that IF you choose to portray a female character, then she HAS to be a positive role model. I think that is absurd, unrealistic, and stifling of creativity.
Today, Gail Simone posted a response to an anonymous question on her Tumblr addressing this very thing, and her response is highly rebloggable:
No one is ever asking for all females to be perfect avatars of all good things. Most sensible people are looking for a SPECTRUM of qualities for female (and other gender specifications) characters.
We want bad girls and good women and selfish ladies and caring mothers and terrible daughters and nasty wives and sacrificing girlfriends, we want villains and heroes and supporting cast members.
There’s no ‘wrong’ female character or scenario, it’s all purely in the execution.
Yes. It’s in the execution.
Write any kind of character that you like, that fits the story, that is creative and honest. Write every kind of female. Write lots of female characters. Then maybe we will get to a point where there is something for everyone, and she won’t have to be everything to everyone.