Well, you can do that already. It's the existing business model.
This is an alternative, for consumers that maybe weren't interested in buying a gun that they can only use in GTA:O, but maybe would be interested in buying a gun from [Game A] knowing that [Game B] and [Game C] (which they already play) allows them to use that same gun in their game. And that nobody else can have that particular gun in those games.
The technology (NFTs) is not really the end-all-be-all, it is lubricant which is intended to make the above use case more likely by enticing buy-in that would otherwise be less appealing.
