Why do girls like guys, and guys like girls?

correction; why is it majority? like in the media; in the malls.. why isn't it all 1/3 staright, 1/3 gay/ and 1/3 bisexual (and very little perecnts of other types..) like multi-wise? (strange question, i know.) but one day i just went for a walk in the mall and realized it when i sat down to enjoy a fruit smoothie. there were straight couples pretty much consuming the entire food court; and 1 out of hundres; (literally) there was a gay couple. PLEASE help me.. :) ( i have nothing against it; but why is it like that? i live in canada; so it isn't from the bible belief system; cause we have jews, monks, blacks, bootists; etc here in canada; so what the hell? (is it cause you want what you don't have?)