Early Wheel of Fortune, especially before 1987 is also much different than what the show is today compared to Jeopardy which has never had any real format change in its 36 year history. Wheel from 1983 until the 1987-88 season had the shopping format, and the show did not introduce elements like the current bonus round wheel, toss-ups, Prize Puzzle, the Million Dollar wedge, and other modern elements were not introduced until much later. While long time fans would probably like the walk down memory lane and some would be interested to see what the show was like in its earlier days, most viewers will probably just find it "old" and wonder why so many elements are missing. The vault Jeopardy episodes will look old too obviously, but the game is the same except for the dollar values.
There's likely other reasons they're declining to show vintage Wheel also that have more to do with costs. I've also seen rumors that Pat doesn't want old episodes on because they show how much he's aged.