Poor Production Quality
I loved the show when it was broadcast on television decades ago, but having watched the DVD of Season 1, Volume 1, I was reminded of the poor production quality.
Sure, all shows back then used the same actors in different roles. Too cheap to hire new ones, I guess, and no one cared what the audience might think. In "The Scarface Mob," an unknown actor played Jake the bookkeeper, but for "The Empty Chair," the studio decided to hire the heavy hitter Persoff, who, laughably, obviously had no lenses in his glasses!
In the last season, the studio seemed not to care at all. In an episode filmed near San Francisco, some actors were talking in a field, and in the background modern cars were speeding on the freeway (280, I think)!