It certainly wasn’t for lack of popularity.
Don Knotts won a whopping five Emmys for his role as Barney Fife, the inept yet lovable sheriff’s deputy on The Andy Griffith Show. The wildly popular program got good ratings, but even so Andy Griffith had always had reservations about the show continuing long term.
Despite this the duo had a dynamic on screen that drew the audience in. Andy’s benevolence was no where more apparent than in how merciful he was with Barney- even amidst losing criminals or discharging his firearm indoors into the courthouse ceiling.
The bumbling and constantly-affronted Fife was the comedic sidekick to the mellow Andy Taylor. But, funnily enough these roles were first written with Griffith as the funnyman and Knotts as the straight man. This was to mimic the roles they played just prior to starting the show (in the Broadway production of No Time for Sergeants) where Griffith was the bumbler and Knotts played the straight man. However, after a few tapings of The Andy Griffith Show they realized that reversing the roles was far more amusing in the setting of the small town sheriff’s department.
So, if Knotts had a popular show with awards coming in why did he leave 3 years before the show ended? In 1999, 7 years before his death, Knotts gave an interview about what pushed him to leave. The truth is a little sad and makes you think, “what if?”. His time after the show was spent making comedy movies in five-film contract with Universal Studios so it certainly wasn’t wasted, but Mayberry just wasn’t the same without him.