No such traditon exists. Among others, Theodore Roosevelt (who let everyone know how little he thought of Taft and Wilson) and Harry Truman (who did the same for Ike) broke that tradition long ago.
Yes, the tradition does exist. A tradition is not the same as an inviolate law. It is not adhered to at all times by all men, but ti is by and large been practiced, as it would be by most men of good manners. Bubba is not one of those.