Forgive me some speculation.
One reason that I have heard cited as a source of rising inequality is that there is more concentration of earning power in household with two working professionals. In other words inequality has increased as household breakdown in those with two working high income professionals and single parent homes or others who earn less.
It seems to me there’s more stratification now in many ways like this. As the professional class has grown I think it has become more insular. Professional marry other professionals and rarely associate with bluecollar people. Perhaps it accounts for the greater polarization on political and cultural value as well.
I have nothing like hard data to support this. Mostly I just have a sense of professionals as somewhat insular, and their large number today makes this more possible than when maybe you were the only lawyer in a small town as opposed to one of many in a large urban area.