Because intersexual relations are insufficiently difficult

It's probably a good idea to further confuse the children of America:

Nothing says �child-appropriate material� quite like gender-bending underage superheroes. At least that�s the theory over at the Hub, the network co-owned by Discovery and Hasbro, which is trotting out its latest soon-to-be-dud, SheZow. That show follows the adventures of a 12-year-old boy named Guy who uses a magic ring to transform himself into a crime-fighting girl. Yes, you read that correctly. When Guy says the magic words � �You go girl!� � he becomes SheZow, wearing a purple skirt and cape, as well as pink gloves and white boots.

At this rate, in two more generations, the great societal problem won't be that men are on marriage strike, but rather that large numbers of young men and women have no idea what sexual roles are or how to even go about reproducing in the first place.  It would be hard to design a better system for interfering with normal psychosexual development than the present one designed by and for sexual freaks.