I mean, in the west quite a few bi guys are usually just hesitant because of the everyday homophobia and shame, but as long as it is kept secret and they're attracted to you quite a lot of guys who are officially straight would do something, they're just scared of the shame.
Of course there are absolutely straight people, but it's definitely not 99%, recently I've read about one study where like 20% of people between 18-25 in the US think they're not straight.
Now, with people who come from arabic or islamic countries it's different, we are not talking shame there, you're completely ostracized if you are every outed, in some of those countries you'll go to prison, where horrible things will happen to you if the other inmates find out you're in there because you're gay, and in some you're either executed by the state or by a mob, or by your family if the shame weighs too heavy.
It's not a surprise that gay or bi guys don't come out there and never take the risk, there are even those who act as if they are gay but then they betray you once you are outed to them, it's scary.
I absolutely understand that people from that culture don't take unnecessary risks, it's like europe 500 years ago, the risk is just too great so if you're bisexual you stay with women and if you're gay you suppress it because you got survival instincts.
