The networks were either expanding soap operas or filling daytime slots with reruns of primetime sitcoms or talk shows (remember Regis Philbin's short-lived NBC show?), which meant even less time for game shows. Some of the newer ones tried during that time - like Battlestars, for example - came and went quickly.
This, too. And in the late '70s, once soaps started expanding to an hour, it was an all-out war to keep viewers glued to a show, so the shows would start at different times in the afternoon - no 3 networks had the same tactic. Check this out from March 1979 (start times only)
ABC: 12:30, 1:00, 2:00, 3:00-4:00
CBS: 12:30, 1:00 (local/Y&R), 1:30, 2:30, 3:30-4:00*
NBC: 12:30, 1:00, 2:00, 2:30-4:00
All soaps, except for CBS's 1pm offering if not Y&R (some stations still carried it at noon) and 3:30 as it was a sitcom rerun (M*A*S*H until September, then One Day at a Time)
CBS jumped on the "12:30, 1, 2, 3" bandwagon when Y&R expanded to an hour in February, 1980. When NBC scaled back "Another World" to make room for "Texas" in August, 1980, they, too, went with that strategy.
CBS dropped out of that programming tactic in June 1981 and never went back to it again but ABC and NBC kept it.