How come people don't believe that I'm Hispanic?

Seriously, It is so annoying. Whenever I am talking to a new friend and they say, 'Oh i'm from india, china, Arabia, Israel, etc.", I say, "Oh, I'm Colombian" Then they just look confused, some even think I'm joking at first. It's just that my physical features are very American. I have freckles, light brown hair, very light skin, etc. My name also throws a lot of people off. Matt is actually short for Matteo, not Matthew, which is common in Spanish-speaking countries. Johnston comes from my great-great grandfather, the only Brit in an otherwise Latino family (Just look at the other surnames: Sanchez, Hoyos, Pati�o, Vargas, Velasquez, etc.). Also, this I actually find insulting, people say I don't act Latino. They say I'm so smart, strict, responsible, never smoked and drink very little, wealthy, successful, studious, and a hypochondria. I get very angry when they say that! Not all Hispanics are like on television, those heart-breaker druggie plumbers! Seriously, why are these stereotypes there? My father was an unbelievably wealthy orthodontist, so was his father! while my mother was only a housewife, she studied Business and Economics. And my other grandfather was the CEO of his own business (Now retired). Why are these stereotypes there?!