In part, because this country has a history of applying the "one drop rule." Meaning that if you had one drop of black (or Indian or Hispanic) blood you were listed as "colored."
That is a fair answer.
What it has evolved into is a racial spoils system where all groups snap at each others face while each of them is trying to be the first to scale the greased pole to the top of "Victim-hood."
As my daughter was filling out college applications, we had to meander through countless, countless links and on-line forms dealing with race.
Race has become the biggest scam and shake down in the history of this country.
But, "Whites Need Not Apply."