I occasionally listen to one of the local radio stations play old Casey Kasem Top 40 shows from the 1970s on Sunday morning, and I've noticed that a fair amount of decent music from that era isn't being played on current Classic Rock stations. I suppose it has something to do with acquiring the rights to use it, but it's still a shame. I think they could benefit from a little more variety, even if it means cutting back playing Fat Bottomed Girls to three times a day.
On the other hand, a lot of that music is deservedly forgotten. Ex-Beatles in particular seemed to be able to get away with anything. Had one of them recorded himself reading a telephone book while smashing glassware with a hammer it would have made the top 40. To his credit Ringo Starr seemed to realize this; his solo material of the time had a certain I-can't-believe-I'm-getting-paid-for-this vibe that made him more enjoyable than if he had taken himself too seriously. Paul McCartney has taken plenty of heat for his Wings offenses, which were wildly successful despite sometimes being incredibly shallow (Let 'Em In and Uncle Albert come to mind), but John Lennon was not without guilt. Some of his top-40-charting live recordings sound like he had promised the promoter new music, forgotten about it until he walked on stage, then told the band to play a standard rock beat while he made something up. George Harrison didn't seem to be as big an offender, but he also didn't have as much chart success, at least on the shows I've heard.