Why do so many people think Indians aren't Caucasian?

Because most people ociate the word 'Caucasian' with light skin. Actually it refers to the people that live(d) on or near the Caucasus Mountains. There are only 4(?) races, Asian, Caucasian, Black, and I think Mongloid. Indians fall under the Caucasian race. They are only thought not to be because they have dark brown skin.