I don't think it does explain much. It could be that Betty is a poor Lithuanian immigrant living in the slums of NYC in the 1960s, and Jennifer has converted to

I don't think it does explain much. It could be that Betty is a poor Lithuanian immigrant living in the slums of NYC in the 1960s, and Jennifer has converted to Buddhism, but doesn't always follow the vegetarianism aspect of the religion. The problem with the example is that "Betty is much like any other American home cook in 1958" hides the diversity of America. Had Betty been living in New Mexico, there would be green chile on the plate. Had Betty been living in Louisiana then the food would be different still. But by given simple hypothetical examples it's all too easy for us to fill in the details with what we think are the right answers.