Well, there’s a lot of weird complications. Like propagating refunds across multiple stores - you don’t own it here, but do you not own it HERE on this one? And the fact that it’s not really the same product from store to store because everybody’s got their own proprietary cloud saves and achievements and whatever. And then there’s just the technical work of sharing that purchase information between 'em all.
I mean, if somebody pulls it off and makes it really work, cool! :)