The spiel for the next CBS show on the schedule (Search For Tomorrow at the time) was dropped sometime between 3901D (December 8, 1980) and 3963D (January 21, 1981), so basically between John Lennon's assassination and Ronald Reagan's inauguration. Gambit, Match Game '7x, Secret Storm, and Love of Life were the other shows that got a plug. I'd imagine this was done away with to avoid confusion as certain stations aired their own programming instead of the one that followed, and also when west coast stations would air Young & Restless immediately afterwards compared to those east of the Rockies, which would air a Search For Tomorrow (and later Y&R) for another half hour afterwards.