Why is this so hard to believe?

Why is it that a lot of people are unaware of black hispanics. Both my parents are colombians from buenaventura. My mom is mixed with black and my dad is black. A lot of people(teachers at my school, my peers, people at the grocery store ect.)are shocked when they know I speak spanish. I also wonder why black people(african americans)say I'm not black but colombian. And many hispanics tend to tell me I'm hispanic and not black. Just like african slaves were brought to america there were also some who were brought to colombia. My race is black and I'm ethnically clified as hispanic! Why is that so hard for people to believe?