I think part of the reason for having separate boards is "gender politics" about wearing scents. For example, a lot of men on Basenotes want to post about what scents other men have found are attractive to women. There's a prominent sticky thread on the top of the men's board about this, with thousands of hits, isn't there? Sometimes men don't want women to know what they're plotting by way of using scent for seduction, so they only talk to other guys about it. "Chicks dig it" is what men assure other men of, even if they sometimes don't know what the hell they're talking about. Of course it would make more sense to ask women what scents they like on men, and occasionally threads started by men have shown up in the women's discussion asking just this question.
There is a social separation of the sexes, in some cultures more than others, but in all cultures, there are some things that men talk to men about, and others that women talk to women about. That may well be breaking down in our day, and it's cool with me if it is. But it's certain to me that men don't talk to women about women the way they talk to other men about women. I wouldn't be surprised if that was true on the women's side as well.
Of course the names "men's discussion" and "women's discussion" don't mean that people don't read and post across the boards.
I would welcome a common board, but I doubt that most of the members would want to abolish the existing boards.
And I should add that I don't think this is about men wearing scents marketed to women and vice versa. I think it's just that social reality I mentioned at the beginning of this post.
Where do the gay men on the board fit into this? Each one may have a different reaction to this, but for myself, I can say that I was socialized as a male and grew up reacting to women in many of the same ways other men do socially. At some point in my early or mid-twenties, the romantic part of that diverged from the social. Most women I've talked to about this think that socially all men are more like each other than they are like women, largely because of being socialized differently. Gay men or straight men or anything in-between, I'm pretty sure we're all men to them in every way except perhaps in terms of potential for romance.