I've always wondered about this, and tonight when I saw it again it reminded me:
Re-runs of "Saturday Night Live" used to be on Comedy Central, and now are on E! SNL is a 90 minute show, but both networks cut each episode down to an hour. So a full third of the original is cut for re-broadcast.
I've noticed that regardless of the channel the re-runs are shown on, the two musical performances make it into each cut episode. The one I saw tonight had Bruce Springsteen on.
Why include the musical performances in the re-run? If you have to cut something out of a comedy show, why not eliminate the parts that are intentionally not funny?
And you wonder what it is that keeps me up so late at night...