N_D_Radioguy said:
Contractual language guarantees the credits will run any time the program is shown; it's tied into the union contracts for IBEW, SAG, Stagehand & Craftworkers, etc.
Apparently, the rules governing the showing of the closing credits have changed over the years -- at least as it relates to the reruns that show on local broadcast stations (as opposed to national broadcast or cable networks). It used to be the case that the closing credits would routinely be clipped during local syndicated reruns, back in the days when stations also did additional editing of the syndication prints (said editing was usually poorly done) in order to slip some extra commercials in. Then, when you got to the closing credits sequence, they'd fade out halfway through, and right into additional commercials or a station ID.
In the eighties, syndicators started offering syndication versions of shows that were already pre-edited for additional commercials -- and at that point, the "film editing" department disappeared from most local stations. Around that same time (or maybe a few years later), the practice of clipping the closing credits also seemed to go away.
Nowadays, even when the programs aren't pre-edited for additional commercials, the stations still don't clip the credits. Several years back, "McHale's Navy" was running on KFWD/52 here in Dallas/Fort Worth -- no additional editing, credits ran in full without clipping, split-screen, or voice overs. Seeing a program that way again served as a reminder of how annoying all of these practices really are...
It may be that the stations were never supposed to clip the credits, but the rule was just not enforced until after the eighties, but that's just a guess on my part.