They might not be showing them because there might be enough changes and therefore made the shows outdated. E.G the old shows don't talk about the Shrek movie or the Jimmy Neutron movie. Also Nickelodeon studios is no more as is Back to the Future. Also the new coaster will be opening soon and they would have to incorporate that in to the show as well.
If you die hard fans out there noticed that some of the content on the Disney shows was updated when Expedition Everest, the Nemo Show, The Seas With Nemo and Friends, and other attractions were either opened or updated.
Maybe Universal doesn't have the resources Disney has to re edit the shows as they see fit.