In 1975, NBC head Lin Bolen tested the show with focus groups. The result was that none of the focus groups liked riddles, which Bolen listened to. She forced the show to overhaul its format (outlined under the YMMV tab) on the grounds that she would cancel the show if Stewart refused to comply and replace Edwards if he refused to comply.
A week later, Jackpot! was moved on July 7 from the Noon slot it held since its debut to 12:30...and since NBC's daily newscast aired at 12:55, the show had to shave off five minutes.
The 1989-90 revival was canned not due to ratings, but because the syndicator was quickly going bankrupt when the show started production. The whole run was taped in about two weeks.