>>1038087My guess is that while not everyone is bisexual, their numbers are far greater than reported, because a lot of people just don't want the hassle that comes with it, so they identify as straight.
As stupid as it is, a man who enjoys the company of women can hardly even look at another guy without being branded as "duuude that is sooo gaay" so they just stick to women.
For women it's a bit different, because "lesbians are hot," at least when kissing in front of drunk, hooting party people. That seems to give them the social license to identify as "totally bisexual." But once you cross the line into a serious relationship, you get "ohh I didn't realize you were ACTUALLY bisexual/lesbian," and attitudes change.
Homophobia is still pretty deeply woven into the collective (western) cultural consciousness and even if people don't want to participate in it, the little things we do can reveal a clear sense of discomfort in people. The trigger point to the "gay eww" reaction is much further, and perhaps more blurred, for women than for men, and this is interpreted as women having a more "fluid" sexuality than men.