Using that logic. What makes you think the clothing stores that only sell women clothing are wondering "Why don't men shop here?" They don't.
So what makes you think the games companies are wondering the same thing?
#5 on this list: http://www.gamasutra.com/view/news/1...ry_in_2012.php
plus when I look at the lists of workshops and presentations at game developer conferences, a large number of them are about marketing to women and other minorities in the gaming community. Gaming companies are realizing that there is money to be made by including people other than the straight white male.
When (I'm being optimistic today) SGRAs are added, it will not just be good for equality (enough of a reason in my book anyway) but also from a business standpoint.