Smothers Brothers

I was all set to recommend Time-Life’s new set of selected episodes from the famous 1968-9 season of The Smothers Brothers Comedy Hour, for the episodes, the historical value, the still-kinda-remembered — and highly influential on The Daily Show and the like — “Pat Paulsen For President” special, and the Paul Brownstein special features, which include musings by Tom Smothers and interviews with many of the guest stars. (And also Rob Reiner, who started as a writer for the show, as did the late Lorenzo Music.) But one thing puzzled me: why were most of the episodes only 40 minutes long, when an hour-long network show in 1968 would have been at least 50 minutes without commercials?