Blockchain provides a mechanism to trade the token in a standardized way with existing marketplace tools, and without central authority/consent.
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.
But for smaller game studios, you may not be able to do it, due to lack of resources, or lack of a moat, or you're not #1 in the space. Then you'd rather go into a collective marketplace. NFTs allow you to have marketplaces with items that are usable in any game that recognizes it.
This has already happened once. For example, in Gods Unchained (a CCG), you can import a Cryptokitty that you own, to decorate your playing board.
https://www.cryptokitties.co/gods-unchained https://blog.godsunchained.com/2019/02/11/cryptokitties-x-go...
It's kinda like cross promotion between games, in the same way mobile games did cross-promotional ads.
You also see this kind of behavior with Openstreetmaps. Google is #1, so they don't care. All the #2 and #3 players are working together on openstreetmaps to collect their market power to beat #1.
What lots of people on HN don't see is that NFTs are public interfaces for interchangable immutable items with a history that any application can choose to honor for interoperabililty. I think you can use it for more than just art.