My reasons.
I think I always knew I was bisexual. Even as a little girl I questioned what was so wrong about possible monogamy with either men or women. I remember one occasion where I was speaking with my mother on 5th ave in Brooklyn and for some reason the topic of my sexuality came up. I was only ten and she had said "Don't have any crushes on boys yet" like any little girl I responded with "I don't like boys." and my mom had then said something that, as you can see, stuck in my head for many years.
"You don't....like girls do you?"
I had panicked. I didn't know what I should say. I thought about both like that. Although I was smart to say "No, mom I don't like girls" I wonder what she would have done if for maybe in that moment she would have accepted me. I can never tell my mother, I fear. I feel like she would disown me or something in that sense if I ever told her the same way I'm attracted to some guys I'm attracted to some girls. I think she is a hypocrite she is friends with gay/lesbian people and appears to be okay with it, but behind their backs she remembers the Catholicism people taught in the 1970s to her and how "being with the person the same sex as you is a sin"
Even so, it's sad for me. I know my sexuality I don't feel there is a need for me to "pick one side" so to speak, yet I feel so selfish because I know there are people who don't just accept their, um, bi-ness... they feel like they need to pick a side, that bi is just temporary and not an actual sexuality.