Why do some genderqueer, genderfluid, and non-binary get mad when they are accidentally misgendered?

For example I am an intersex woman and I look female and sound female . So why would I get upset when someone assumes I am female? I know you aren’t supposed to assume someone’s gender identity but most people do assume one’s gender based on sexual characteristics such as voice, bodies, hormone levels, etc. why do some individuals get pissed off who live outside the binary of man or woman when someone makes a mistaken assumption. I don’t call anyone miss, ma’am, or sir just because I don’t want to make a mistake..intentional misgendering is rude but a mistake happens and sorry to say it 8 out of 10 times someone is correctly sexed. People are shocked to find out I’m a hermaphrodite because they just think I’m female. But I can’t get mad and pitch a fit because someone assumes I’m completely female. People have eyes and ears to use their senses. Even little kids call me a she. I have been chewed out for making a mistake before.