I think Randy mentioned the reasons behind not including things like this somewhere. I don't remember if was in an interview, the book, or a post here, but...
What he basically said was, he didn't want to include full shows with dialogue because it would not make sense just listening to it. Sure, some of us have seen the various shows/films and would know what was happening on screen, but most would not. I believe that's why he only included the score to America the Beautiful. And with something like Magic Journeys, HISTA or Captain EO, you really do need to understand what is happening on screen with all of the effects and such to get the full enjoyment out of it.
The score to HISTA would have been a nice inclusion, but I'm sure there was a good reason for leaving it off, like rights issues or something like that.