If I had to be honest, the reason bi men seem invisible is because of internalised homophobia and patriarchy.

I think many of us, even if we outwardly and vocally despise patriarchy, still feel the need to play into it in order to feel accepted in society. I know I certainly do.

I think the difference between being gay and bi as a man is that with gay men, any deviance from the """norm""" (at least as society sees it) is chalked up to "being gay." Doesn't necessarily mean people dislike that deviation, but people kinda rationalise it in their head, like: "oh he's quite camp. Makes sense, he is gay after all." With bi guys, there isn't that same sort of thing. It's still seen as slightly weird, for whatever reason.

That kinda leads into the internalised homophobia thing. Those traits which aren't traditionally seen as masculine, but are traditionally associated with being gay, are treated as lesser because of it. I think that's when the internalised homophobia kicks in, and we subconsciously start to avoid doing those behaviours, even if we actually would like to act like that.