Because of the stereotype of gay guys, who, for whatever reason, come out as biseuxal first. Because of the myth that men can only be gay, if attracted to men. Where that comes from I don't know. Because of the stereotype of girls experimenting in college (Lesbian until graduation being meme) or flirting with girls to get a guy's attention. Because some mono-sexual people just cannot imagine being bi/pansexual.
I think it has to do with 'prioritising the penis' and a very bigoted view of gender and sexuality. Bi men are said to be gay- because your liking men makes liking women irrelevant. Similarly bi women are presumed to be straight- because what matters is that they like men. So in both cases, because they like men, and this aspect is seen as more important, the other aspect is not acknowledged. Complete nonsense of course, but this would be my guess.
Probably because many gay people use bi to come out and then feel like gay is a better fit later on. Every gay person I've spoken to has denied/suppressed their same sex attractions from a young age, which is something I fail to relate to. I'm still not comfortable with the bisexual label, mainly because I fear that I'm just a gay guy in denial (also a stereotype). I wish I was 100% gay, then I would know for sure what my attractions mean.
Yeah, this is especially the case of bi men- you can give one blowjob, and you're forever gay to society, even if you sleep with a thousand women afterwards. The same is true to women, they can sleep with millions of women and be labeled as straight. A lot of people don't like to believe women "count" in regards to sexuality unless you're a straight man of course.
Interesting topic. I fully believe that there are both bi men and bi women. I don't think that a man is specifically gay just because he is attracted to men, or because he has had some sort of sexual experience with a man. That would make my partner gay since he has been with a guy during our relationship. I've been with women since I was a teenager on until my relationship now, but if that matches what you all said I'd only be straight correct? I'm not. I love all people equally doesn't matter what parts they have(or don't).
Seeing as I -am- a bi woman, I fully believe im bisexuality. And I am both attracted to men and women physically as well as emotionally. I dont see how anyone can tell me that my sexuality is invalid or doesnt exist. Maybe people just cant understand what they dont experience for themselves?
I suspect there are a number of people who have gone out with someone who labeled as "bisexual" but in reality had not really come to full acceptance of him or herself, and that, in turn, caused problems in the relationship. Additionally, there are an awful lot of people who use the "bisexual" label during the bargaining phase of the coming out process, so many people (wrongly) assume that anyone who labels as bi has just not accepted him or herself as gay or lesbian yet. Regardless of what anyone says, this isn't even remotely in dispute: bisexuality has been described, written about, studied, and understood for decades. For anyone to say it isn't real or doesn't exist is simply ludicrous.
It's less threatening to pretend something as commonplace, resilient, and natural as bisexuality simply doesn't exist than to reconfigure your own beliefs and biases. The vast majority of people identify as being monosexual in some way (straight outside the LGBT community, and gay within it). When people view sexuality in terms of "tribal" allegiance, bisexuals, pansexuals, etc. can seem like foreign spies. Especially with men, where your sense of masculinity is so fragile, and "gay" is one of the worst things you could be, akin to being a woman. You're practically walking on egg shells 24/7! Anyway, anecdotal experience, stereotypes, homo/biphobia, and sexism all play parts in people denying bisexuality exists.
Just to echo what Chip said, bisexuality does exist - whether people "think" so or not. Any argument leveled against bisexuality could easily be taken against hetro or homosexuality - and most people accept that they exist!
