Why is looking at income disparity okay, but not other disparities? I understand a less stratified and segregated society provides a better life for everyone,

Why is looking at income disparity okay, but not other disparities? I understand a less stratified and segregated society provides a better life for everyone, and do think that education is the tool to counteract bias. There’s typically 5 types of stratification, economic, social, gender, race, and ethnicity. To just choose economic as the only focus really does not make sense to me.