I think that the women in this game are sexualized because it's titillating. I find strong looking males and sexy looking females more exciting than their bland, normal, or ugly looking counterparts. It really doesn't matter whether they are sexy; It matters whether they are fun/exciting to look at.
Video games are played to have fun. I find sexy women more fun than old, fat, normal, plain, or very young women. I find that in men I have a wider range of what I like looking at.
I find the argument for having sexy men much more compelling and reasonable than the argument for having un-sexy women. But as a man, I don't find sexy men compelling. I won't EVER buy a male skin because it's sexy. However, my female friends do find sexy women compelling. Really, I think EVERYONE finds sexy or sexualized women compelling, whereas fewer people find sexy men compelling. I think sexy women skins will sell more than sexy men skins.
But that's just my opinion, feel free to disagree.