Do you find women sexually attractive? Do you find men sexually attractive? I personally find women attractive. I can't imagine thinking one day, hey, I'm going to have sex with a dude, because it's outside of social norms.
Do you think that with all the bull **** gay people have to put up with that 10% of the population would willfully make a choice that goes against their biological nature? How about 70 years ago when getting caught in a gay relationship could land you in a god-damned psych ward?
Explain bisexuality? Some people are turned on by women and men. It's not !@#$ing hard to explain.