People choose to vote for / elect people who are willing to implement various policies to achieve it. What is acceptable to the population is (partly?) determined by the norms of that population and society, and the acceptance of various ideas will determine what politicians will campaign for.
Japan's economic system was crafted in post-war reconstruction by General MacArthur. It's literally the furthest you can get from "social norms precede policy."
You think the distribution of living standards across a population could be a matter of social norms? How?