It’s all about narrative. After you’ve been doing heavy lifting with Luke, Leia, Han, Chewie, Lando, the droids, and all their friends and allies for a couple of hours (even the ewoks), and they’re ready for a final celebration and goodbye, you don’t tell them to hold on and wait a few minutes, because you need to wander around the galaxy and peek behind the curtain and see what these other planets are up to who weren’t even in the rest of the movie.
That doesn’t even touch on the fact that some place like Coruscant, for example, is not going to be celebrating the destruction of its own military forces.
Return of the Jedi is the characters’ story. The ones who actually appeared in the movie. It’s not George Lucas and the universe of Star Wars story. We don’t stop the movie so we can devote pointless camera time to random creatures that pop out of walls but have nothing to do with the story. We don’t fly off to fifteen different planets and subtitle each one of them just so we can make new Wookiepedia entries and masturbate to them in our sleep.
We just don’t do those things. We stay with our characters and our intimate setting and that’s the story.
While characters are one of the most important elements of the story, they are not the sole element of the story. One of the major elements of the trilogy is fighting the tyranny of the Empire. The celebration/uprising scenes do not show just some random planets. In addition to the capital planet, which has strong symbolic value in this aspect, the scenes show us very familiar places like Tatooine and Bespin, both of which were occupied by the Empire during the story of ANH and ESB.