DungeonMasterOne said:
The issue is a social one. We still have a very patriarchal society with long-standing and very sexist ideas of gender roles. While things are finally improving with legal changes that at least outlaw direct discrimination against women who want to do non-traditional occupations like soldiering or engineering, there's an immense amount of inertial in people's general ideas of the roles men and women should have (and should not have), and those extend into most areas of life including sexual ones.

At core, probably a similar number of women would enjoy getting deliberately messy as men do, however while men grow up in an environment where kinks and fetishes are at least expected and tolerated under "boys will be boys", women are still often expected to regard sex and sexuality as something to "put up with" in marriage, not something they should be actively into themselves. Think of the terminology - a man who has lots of sex is a "stud" or "sowing his seed" and seen as someone to look up to and admire. On the other hand a woman who likes sex and has lots of sexual partners, or is into kinks and fetishes, is seen as a "slut", someone to look down on, someone dirty and degrading, going against God, etc, etc.

And then on top of that, consider what happens to any woman who does put her head above the parapet on fetish sites like this one - she gets her spirit crushed by aggressive horny guys who see her primarily as a sex object existing for their pleasure - and yet who then freely pirate her work, wilfully degrading her.

While lots of models are only into WAM as a fun (non-sexual fun) thing to do - they enjoy the chance to play in mess, get messy, mess someone else up, but only from a "this is awesome fun esp when we also get paid for it" POV - there are also models who genuinely are into WAM as an actual fetish and get genuinely turned on by having their panties filled with custard or being made to sit on cakes, and can and do get messy for their own pleasure as well as on camera. But many such women actively avoid taking part in on-line fetish communities, or just hang out anonymously, or with male profiles, and little or no active participation, to avoid the hassle they'd otherwise get.

Basically if we want more women to participate and be public as active fetishists, we all need to make an effort to treat women better in general. To quote a current meme, there's a good reason many women chose the bear.