Why are Latinas thought to be curly-haired?

Seems like curly hair is umed to be an ethnic trait, even though Asians have the straightest hair of any race. Even many white girls with "straight" hair have a slight frizz and or/wave to it. Most Latinas I know have straight hair - I'm mixed Latina/white, and have just a slight wave to my hair. I go to this site for women with curly hair (mine used to be curlier than it is now. It's straighted out over time). White women there complain that they're mistaken for Latina sometimes becasue of their curls, that curly hair is an ethnic trait. I don't think most Latinos have curly hair, though there are few where I live. Why is there this umption that straight hair is a white trait? Look at Irish ppl with red curls, and my Czech grandma has natural curly hair. Is it because black people have curly hair, and whites consider themselves opposite of them, and WANT straight hair to be a white trait?