Why were there multiple repeats of the musical numbers?

Hollywood Canteen is one of my all time favorite films, I first saw it back in 1980 and I've seen it countless times. I never get tired of it.

One question I have is why some of the musical numbers were repeated multiple times throughout the film. For example, Don't Fence Me In was first performed by Roy Rogers and the Sons of the Pioneers. Then the Andrews Sisters sang it again a short time later. I know the sisters had a big hit with the song, but I've never understood why it was repeated.

And then Sweet Dreams, Sweetheart was played three times (or more). Once with Joan Leslie on vocal, it's played as the background score throughout several scenes, then Kitty Carlisle sings it. Again, Ms. Carlisle had a hit with the song. And I can see that this tune was Slim and Joan's song, so this likely had something to do with things.

But typically songs are not repeated in a musical, so I've always wondered.