What am I missing with this?

Mill Creek has been licensing a bunch of series that have already been fully released on DVD. It seems to be many of the series that were originally released by Anchor Bay/Starz and are now out of print. The only advantage I can think of with That 70s Show specifically is that there were some musical replacements on the original releases, but I find it hard to believe that a company like Mill Creek would have the resources pay for the original music. Your guess is as good as mine.