What you need is a bisexual visibility movement, which I guess what involve more people coming out like you have -- kudos on doing it so early, btw -- and sticking with it. You hear of people identifying as bi for a brief period -- especially as a way of coming out on the installment plan -- then ultimately "picking a side."
I don't think this is always due to pressure from big, bad monosexuals. Sometimes people meet the love of their lives and settle down with that person, and if the relationship is monogamous, I'm guessing they find some way for that other side of their sexuality to not matter so much. Or they just quietly seek satisfaction where they can find it.
Certainly a lot of bi-identified guys seem to be really, really into discretion, which isn't very conducive to a political or consciousness-raising movement.
Out of curiosity, OP, how many openly bi people do you personally know?