Hey, what's going to happen to the demo when you send Ash-Greninja over to Sun & Moon? Ash-Greninja is your only Pokemon. Like will Professor Kukui lend you his Pikachu? Like sure at that point you don't need the demo anymore aside transferring any items you didn't yet, but still that doesn't mean they shouldn't plan on someone showing off (finished) demo to someone to maybe convince them to get the game or show them some Pokemon history.
Actually that's another small disappointment I have from both the ORAS and SM demo, once you play through it it's done. It's not like with the normal games where you can restart it, I think you gotta delete it if you want to see the "story" stuff again (thus if they remove the demo from the shop that means its "lost" unless you can hack it). Wouldn't mind if they can let you sort of restart the demo, minus getting any transferable items if you already got them.