I think in large part it's that it's uncomfortable for white people (I am one myself) to talk about race especially in subtle fashion. It's relatively easy when it's something like do black people have the right to vote during the Civil Movement (easy in terms of people being able to fire hoses turned on blacks for example) compared to modern vote suppression tactics. Likewise it can be hard to understand how a multi-millionare athlete who has so much money can be on the receiving end of racism.
I think part of it is actually a symbol of how far we've come. We've gotten past the days where a large percentage of people were okay with "segregation today, segregation tomorrow, segregation forever". Instead our societal racism is more subtle. That's good in that people now understand that racism is a bad thing, but it's hard to fix because people are invested in not being racist, but think of racism as just the overt things.
It's similar in how guys will admit to rape if you ask the question "Have you ever coerced somebody to intercourse by holding them down?" nearly 1 out of 3 guys will say yes, but the number drops substantially if you ask "Have you ever raped?" We're very good as a species at justifying our actions to avoid the words we know are bad, but not as good at looking at our actions objectively.