Really great questions Ryan. One argument for why we should think about the "how" is that it may offer more insight into opportunities to interrupt the mechanisms creating inequality. Sure- sometimes we can change exposure and interrupt consequences without understanding the mechanism, but often our options for intervening are constrained and the more we understand about how a social exposure becomes embodied, the more opportunities we have to interrupt that process. Another argument is simply that people find biological explanations more compelling than non-biological explanations (I don't know why but my impression is that this is true). So as a mechanism for motivating political commitment to reduce inequality, it's useful to be able to explain the biological mechanisms. Finally - and this relates to the intervention argument - sometimes understanding the biology helps us evaluate whether certain things are really causal. We cannot randomize poverty, but having a biological understanding of how poverty causes diabetes risk (for example) helps us be sure that it is causal rather than resulting from confounding.
Maria