As I said, we carry the show as nostalgia. The problem, of course, is that Premiere presents the shows as they originally aired, except for combining segments so as not to duplicate the original format of six breaks an hour (which you and I both know would never fly with listeners now). There is a logistics problem with trying to reformat it to eliminate the less familiar songs ... especially since we don't have Mr. Kasem around to cut any new voicetracks.
And as far as I can determine from the affiliation contract, we're not supposed to re-edit the show ourselves, other than deciding whether or not to play the optional "extra" every hour. I don't think most individual stations have the production time to do it, and Premiere certainly doesn't seem eager to do it either.
Not to mention that, depending on the chart for the week being played, the number of songs that might deserve to be excised will vary.
The guy who remastered the series for Premiere, Shannon Lynn, maintains a website with the original cue sheets for every AT40 that originally aired (even the ones with guest hosts that Premiere never sends out). Here are the cue sheets from his site for the past two weekends:
October 9, 1986
October 13, 1984 (you need to scroll down to page 10 for the cue sheets, because whenever Shannon has the original production notes he has included them in the PDF)
How would you edit and condense those without it sounding completely disjointed? I don't see an easy answer.
And this is only the 80's shows. Premiere also syndicates the ones from the 70's, which probably have aged worse.