No idea why PP&M never appeared on Ed Sullivan, but I do wonder whether political concerns (on their end, not the show's) were involved. Someone already mentioned CBS's informal blacklist of Pete Seeger, which was not broken until the Smothers Brothers fought to have him on their show in the 1967 season (and, even then, one of his songs, "Waist Deep in the Big Muddy" was filmed but removed by the network, not to be successfully shown on air until it was re-fillmed for the Smothers during the 1968 season, by which time anti-Vietnam sentiment -- if certainly not still welcomed by the networks -- was at least much-more ubiquitous and difficult to suppress entirely.) So, that was a CBS-wide issue that may have affected the trio's decisions regarding Sullivan.|
But, there was also another issue with Ed Sullivan and folk musicians, and that was Bob Dylan's walkout from Sullivan's show in mid-1963 after he was told he could not perform his anti-John Birch Society talkin' blues on air. ("Talkin' John Birch Society Paranoid Blues"?) While the performer boycott of "Hootnanny" was pretty conspicuous because it was a *folk* program -- i.e., one profiting commercially from the folk boom -- that very specifically would not allow the father of the Folk Boom to play, the sensitivity of performers was by no means limited to that one show. Sullivan certainly would have observed the network's blacklist of Seeger, and the Dylan matter -- which was widely covered at the time in the general press but particularly harped upon in the Sing Out/Broadside niche of the press that catered to the folk community -- could not have helped matters.
I'm trying to think through PP&M's 1960s major TV appearances to recall if any were on CBS until the Smothers Brothers in 1969 (the same season as the successful Seeger airing, but after it.) I can think of appearances on ABC (77 Sunset Strip, Jack Benny, Bandstand), NBC (Roger Miller, Andy Williams, Jonathan Winters, the Tonight Show) and syndication (Lloyd Thaxton), but I'm not immediately recalling a CBS appearance until after the Smothers Brothers broke the Seeger blacklist. Perhaps I am (a) forgetting some appearance; or (b) just observing a coincidence. Or perhaps this is just a function of the fact that Sullivan was the only really big variety show CBS presented during those years until the Smothers Brothers. (There were smaller, short-lived ones like The Entertainers and Carol Burnett, but nothing of the panoply that appeared on the other networks. Ed Sullivan was, most certainly, the sun at the center of the CBS entertainment solar system in those days.)
Anyway, I wish I had a definitive answer, but it's certainly an interesting topic in any event.