Old Radio Commercials as history

Some radio historian has probably written about old radio commercials as a history of the times in which they were aired.  Here's one I heard last night on a "Great Gildersleeve" show from 1949. Sponsored by Kraft, makers of  Parkay Margarine, it told us that we could now buy colored margarine if our state was one that had made it legal.  But it would cost more because of a federal tax on it. No doubt that made no sense to any  present day youngsters under 70 or so who might have been listening. I remember when "oleo," as  we called it, had to  be sold  in its natural white and colored at home with a little packet of yellow coloring that came with it.  The dairy industry didn't want the margarine makers to fool us into thinking we were getting the real thing..  Some parts of the world were behind us in accepting the yellow non-dairy spread. .  Australia didn't legalize it until the '60s.