I have a vague recollection of most game shows in 1980 taking time out of the show to make a public service announcement to return your census form. The one I can best recall was Bill Cullen on, I believe, "Hot Potato", but I know other shows did as well.
I searched Youtube for some of these PSAs, but came up empty. Did any of these air on GSN, or were they edited out? It's an interesting little time capsule of the era.