Some possible explanations based on research and literature. Some of them are:

• Implicit bias: Implicit bias refers to the unconscious attitudes or stereotypes that affect one’s understanding, actions, and decisions in an unfair manner. Some non-black people may have implicit biases that associate blackness with negativity, inferiority, or difference, and whiteness with positivity, superiority, or normality. This may lead them to emphasize the race of black people as a way of highlighting their perceived difference or deviation from the norm, while ignoring the race of white people as a way of assuming their similarity or conformity to the norm.

• Colorblindness: Colorblindness is the ideology that ignores or minimizes racial differences and pretends that race does not matter. Some non-black people may adopt colorblindness as a way of avoiding or denying racism, or as a way of expressing their good intentions or egalitarian values However, colorblindness can also have negative consequences, such as erasing the identities and experiences of people of color, ignoring the systemic and structural inequalities that affect them, and perpetuating the status quo of white privilege and dominance. By describing someone as black and not as white, some non-black people may be revealing their colorblindness, as they may be implying that race is irrelevant for white people, but relevant for black people.

• Lack of awareness or education: Some non-black people may simply lack the awareness or education about the history and implications of racial labeling and categorization, and how it affects the lives and opportunities of people of color. They may not realize that describing someone’s race only when they are black and not when they are white can be seen as a form of microaggression, which is a subtle, often unintentional, form of discrimination or hostility that communicates negative or derogatory messages to people of color. They may also not be aware of the diversity and complexity of racial identities and experiences, and how they are shaped by factors such as culture, ethnicity, nationality, language, religion, and more.

These are some of the possible reasons why some non-black people would describe someone’s race only when they are black and not when they are white. However, the preference and decision to use racial descriptors may depend on the individual’s context, purpose, and choice.

https://www.rd.com/article/black-or-african-american-which-term-you-should-be-using/.                                                                                                                                         https://goodmenproject.com/ethics-values/when-is-it-ok-to-call-someone-black/                                                                                                                                               https://www.cbsnews.com/news/not-all-black-people-are-african-american-what-is-the-difference/                                                                                                               https://goodmenproject.com/ethics-values/when-is-it-ok-to-call-someone-black/