My mother, who was a girl during WWII but did have easy access to butter, switched to margarine after the war when it was marketed as some sort of luxury food! To this day she still uses it, applied to her toast or bread about half an inch thick! When I stayed with her recently, the first thing I did was buy some butter for my needs.
Still, she has just turned 90 and is fit and well. It must be all the preservatives!