Mostly because the roots of every discrimination are basically the same, and if you focus on only one aspect of it, you will not succeed no matter how much progress you think you're making. For example, both racism and misogyny is based on the old entitlement, on the old white men's unearned sense of superiority, and if you don't target that, you will never have an egalitarian society, even if you make them pretend that they aren't overtly misogynistic anymore. It's like TERFs teaming up with white supremacists to harass trans people, only to be incredibly surprised that white supremacists hate women too.