That's really interesting. I can see some factors from experience: even more than invisibility, maybe it's about how much they're dealing with *men,* ...the fact is a lot of straight men can be pretty insecure about having a bi partner: most notably, if they're a possessive/jealous type, they tend to be jealous about you interacting with *anyone* ...in large measure because of ingrained bi-phobic prejudices on top of the usual: the idea one's particularly promiscuous, always on the prowl... that you might be 'turning gay' any moment you're not interested in sex right now... even that you're just somehow 'lesser' than straight people as per usual, etc.

That can add a ton of relationship stress right there, sometimes things get kind of abusive, ...and that alone can lead to long-term anxieties and all.

Coming out/early life experiences can be kind of complicated, too... Just cause you're attracted to men, too, doesn't necessarily mean you 'read' as 'straight,' and in a world of binary thinking and homophobia, it can be that much harder to figure yourself out.

It's probably about the particular kinds of stresses we go through, in part, I should think, and indeed a lot of the insecurity *around* us, particularly when it comes to a lot of the menfolk.