Because people believe that social class is your own fault. That people can just pull themselves up by their bootstraps if they weren't lazy. Not that I agree with this.
This. In US especially, the thought processes around race are just ...catastrophically delusional due to our terrible history with it. And by that I mean it seems to reduce us to rituals like DEI because we simply are terrible at reckoning with it in meaningful, material ways.
But the resistance to dealing with race and class together is real, in part because class is seen as individual problem. Race is seen as more cultural, systemic, or the province a minority running around with sheets on their heads.
I've personally only seen strong efforts to dissect them both, in earnest, at the same time, in the margins of society.