Why does "ethnic" or "cultural" always refer to something non-white?

This is a race question, yes. This is not flame bait.

I genuinely want to know why this is – when we live in a multicultural society. “Ethnicity”, “ethnic”, “cultural” – these words always refer to a non-white group when uttered or written.

It’s a subconscious nuance that whites tend to not see.

Please let it be known that although my wording has been generalized, my intent has not. This is a disclaimer – if it does not apply to you then it does not apply to you. I’m just asking you to step in someone else’s shoes to answer the question.