To be quite blunt, if you're a heterosexual female and you've dated, at some point you're probably going to be with a guy who thinks lesbians are awesome (this is, of course, the airbrushed, porn-movie view of lesbianism - two hot babes willing to get it on with each other slowly and precisely for a man's pleasure, and then happy to have him in the middle, as well). It's not a big secret that it's culturally OK for men to wax poetic about lesbians, but it's not for women to talk about their voyeuristic m/m fantasies.

Now, flash forward to most of the women doing the slash fanfic writing; my guess is old enough to have dated and known a few men, heterosexual, some even married. Tell me WHY they would waste their precious private alone time writing their husbands'/boyfriends' lesbian fantasies, which I'm sure they've had to hear about from more than one man in their lives, and not their own - which they're probably discouraged from discussing openly very much, if at all?