The purpose of this post is not to imply that bisexuality doesn't exist. It's to clear up a few misconceptions surrounding the popular notion that "most women are bisexual". This phenomenon started around the year 2000, well after my formative years, so I've always been suspect of it.
First of all, it is important to note that according to US Government statistics, only 0.7% of all adults identify as bisexual. This percentage goes up (a little) when it comes to Caucasian women 18-30, especially in progressive areas, college campuses, and those who work in the sex industry (porn and strippers). But that's cultural influence, not biology.
Also, the influence of porn is quite substantial. Couple that with the entertainment industry's use of it as a money-making tool, both these things have normalized this phenomenon to the point of it actually being ingrained into our culture.
Also, many women think this what men want. However, it is such a psychologically lazy way to garner male attention in order stand out in the dating pool. Perhaps they feel they have nothing else to offer, so they play this up.
Let's get into the 'studies'. The studies are done by horny old men, very small sample sizes, and tons of selection bias / confirmation bias. They show nothing other than women being aroused by the act alone. It does not show them being sexually attracted to the participants of that act. Otherwise, they would be chimpanzee-sexual as well, since they show arousal by chimp sex, too. 'Nuff said.
There are guys who obsess about this daily. Some are excited at the thought of all women being bi, others are very insecure in their manhood, and worry about the opposite sex finding them attractive.They watch too much tv, and too much porn, and don't get out and socialize with actual women.
The internet is generally a liberal and progressive place, especially sites such as this one -- plus we skew younger. And bisexuals generally flock more to the sex topics.
In reality, women are hardwired to be sexually attracted to masculine features and attributes, so the idea of most (or a good percentage) of women being bi falls on its face. Many young women (especially the hypersexual ones) are brainwashed by the popular culture to think they are bi, and that it's even the "default".
Are there bisexual women? Yes. But it's not most, and it's not even a high percentage. The cultural factors I just mentioned shape our perception of reality.