Because most Central America countries are way homophobic. And they are too square about sexuality, if you are masculine you are straight, if you are effeminate you are gay. Vice versa for girls. And really, having to explain what a bisexual is to 3/5 people and then being called indecesive, greedy or in denial is just not worth it.
Most of the time, they hold the answer within themselves, after they explain their situation, it's obvious to everyone, except them. But only the person can decide their sexuality, and I'm in no place to start labeling people. You can label yourself.
I don't see were the word 'all' came from. I bolded the pronoun for you... You can't go around generalizing people based on one person and some stereotyping. Everyone is different and sexual orientation doesn't go hand in hand with anything.
By everyone? weird place. I don't know if they were jealous or whatever, but hey, you both are in a relationship and you are both happy, so, hell to them.