And when you take a gander at many of the costumes out there, it's no wonder! Halloween is the one time of year where it's socially acceptable for women to run around being as trashy as possible. It's the only time of year women are thoroughly encouraged to bare as much as possible, to look as slutty as possible, and to attract as much untoward attention as absolutely possible.
Girls pick up on that and want to emulate this horrible trend earlier and earlier. Costume makers aren't helping with their shorter hems, tighter, form-fitting fabrics and "asset bearing" styles. And of course, you've got popular shows like Toddlers and Tiaras highlighting this seriously disturbing trend with such glitz and glimmer we've got no one to blame but ourselves.
C'mon now. They're kids! Why do costumes like this even exist?! *Grumble grumble grumble*
Thank God I've got a little boy at this point. If I'm ever blessed with a little girl, I don't know what I'm going to do with myself when the time comes to slam the door shut on this one. Eeps.