Why do people still think there's a certain way to "act" straight or gay?

ok well, why do people still tend think there is a certain code of behaivors, intrests, beliefs and personality types that automatically have to coincide with one's ual orientation????? i think it's so frustrating!!! some people have told me they have umed i was gay because of the way i act or who i am friends with, and some people act shocked to learn i am not straight, because i didn't "act" gay enough??? wtf??? i don't get it. actually i am , and i have friends of all orientations...who cares??? i guess people still judge uality in how masculine or feminine one is. i know all kinds of gay people, straight people, and people, and not one is the same. it's like we're supposed to get some manual to study and follow to proove our ual orientation. i'm so tired of it. does anybody have any expierences of someone making umptions of their s.o. based on they way you act, your intrests, or who your friends are that weren't completely accurate? and how do you respond to it? thanks for the feedback.