Maybe it’s simply because when they look in the mirror, what they see looks more like a black person than a white person? Honestly, if you didn’t know for sure the celebrities in question were multiracial, and just saw their faces for the first time, what race would you associate them with?
In the case of Keys, she looks Hispanic to me.
I knew 2 people long ago, 1 male 1 female that were passing as white. The man looked hispanic, although his mother was caucasian and his father black.
The woman was fair skinned, mother caucasian, father black.
When I asked the woman why, she did not want to be known as bi-racial, she in essence said she did not need the baggage that being bi-racial entailed.
When I asked the man same question, he indicated that he would rather make his way without all the crap that went with being black.