Back in the old days the first act was just the show open, monologue and meet the families.
Not to pick nits, but I've never seen an episode where this was the case. The '76 shows I'm familiar with had one question before the first break.
These days, I wish they would put the commercials after each of the first two questions, and play the rest, legitimately, in act three. I think the move towards really long first acts (on Feud, Price, and other shows) is to discourage tune-out, but given the popularity of the show, I don't think people are leaving after one question, particularly if you stack that one to be the most eye-grabbing.
-Jason