It’s probably because systemic racism is a bit more covert and insidious in nature than overt racial discrimination. But just because it’s not obvious doesn’t mean it’s not there. However, one could argue that racism in the US is actually quite overt and obvious. It isn’t unexplainable factors, they’re just factor’s that those in positions of power do not want to pay attention to or don’t appreciate or understand the need to. It’s things like recognising the impact that intergenerational trauma has on individuals, their families and also their wider community. It’s things like poverty. Or over-policing of poor/black communities. And it’s also about how all these different issues intersect and further disadvantage people.