I'll go out on a limb here and wager that I am the only person in this thread who actually has firsthand experience with this subject. The converts I know are in fact mostly women, none of whom converted for the purposes of marriage. If I were to guess at a reason, it would be that women tend to find themselves marginalized in society to a much greater extent than men, which might lead one to seek out religion. I think it's worthwhile in this case to examine social expectations placed on women, but I couldn't comment further on that, seeing as that I am not a woman.
I was hoping you'd chime in (and also looking for confirmation if those reports of the numbers are indeed correct.) Thanks.
In regards to Beet's comments:
1-Anyone who seriously thinks atheists are more gender-progressive needs to consider that Red Pillers are almost exclusively atheist and
2-In regards to Islam being sufficiently feminist, how many female imams exist? Are they allowed in any other than a handful of breakaway sects?