I'm not sexist and I don't want to come off that way, as all girls are different, but I've also noticed that generally the same is true with girls and music as well. Most girls tend to listen to generic top 40 music unless their bf turns them on to good stuff.
It probably has a lot to do with society and how girls are treated growing up. I could probably go on some sociological ramble, but i'm not in the mood.
Like the name Icculus... I'm hampton bound in a few days myself
This tends to be more common than the converse in my personal experience, but I think this has more to do with the different societal pressures males and females face in their formative years. Especially in the south, which is where i currently reside. Obviously this is not a hard and fast rule, that would be a ridiculous assumption, but there does seem to be more societal pressure on females to be "normal." I have no idea why this is, but it seems to be the case.
It also may have something to do with the fact that people identify more easily with people that they percieve as similar to themselves, and the preponderance of the major figures in the psychedelic movement are men. Hoffman, Leary, Owlsley, Keasey, McKenna, Shulgin, Hunter Thompson, are more likely to have greater influence on men than women because they're all men.
I know plenty of females that enjoy psychedelics, but I know far more males that are into them, and I know almost no females that share my, and several of my male friend's penchant for ingesting strange chemicals in the dead of night alone. I'm not saying they don't exist by any means, but I've observed far more male psychonauts than female.
All this being said, I'm only attesting to my own experience, and I'm certainly not trying to down women, and I don't think it will seem that way. I'm also fairly certain that this trend will likely change with time.