Could it be because of music clearances? When showing classic clips, Wheel often dubs over old theme songs and cues, though it seems they should already have rights to all of it.
That being said, part of the fun of Classic Wheel is that the puzzles were often relevant TV shows and celebs, not to mention Vanna's wardrobe or the prizes. Really hope they choose to show some classic nighttime Wheel at some point, because I think that's the kind of stuff that could go viral and create some positive buzz.