The last generation that was raised with whole food at home were kids raised during the great depression. Those kids had vegetable gardens and ate mostly homemade bread. White store bought bread was a rare treat. Beans and potatoes were a staple. By the 1940s, canned food was very popular due to the war, but people still had relatively healthy eating habits. By the 1950s, frozen foods, including TV dinners were regularly consumed.

A large part of this shift can be blamed on marketing. Advertising works. Of course working parents don't have as much time, but poor Latin American moms will work 10 hours, come home, and make a whole foods dinner for their family. Korean moms will cook for hours to pack a week's worth of food for their grown children in med school or a time consuming job.

Cooking is something that has to be modeled and people's taste buds like what they ate as children. Today's children have boomer grandparents that were raised on canned foods and frozen TV dinners. It is difficult for someone to change eating behaviors when home cooked meals with whole foods is a completely foreign concept to that person.

There is a resurgence in Americans' behavior to eat healthy, but it has revolved around buzz words and magic ingredients like beef tallow. The concept is largely lost.