James Herriot mentions in one of his books that it took him a while to get accustomed to the fact that Yorkshire farmers ate their meals in complete silence.
As a Glaswegian he had been brought up to converse politely at the table, so it is or was obviously a regional habit.
The "either butter OR jam, dear, " rule came into play whenever my parents were, or felt they were, short of money, which happened with monotonous regularity in my childhood home, and embarrassed me horribly when school-friends visited, as did my mother's rule that we wore slippers indoors and APRONS!