So, the use case I'm thinking of is more along the lines of non-cosmetic assets. Take FIFA Ultimate Team, for example. The way it works currently is that each player in the game has one or more "cards", or sets of stats. Special versions come out all the time which have significant impact on gameplay.
FIFA has an in-game market where you can buy/sell/trade cards, for in-game scrip. Want to sell your special Killian Mbappe card you just pulled? Congrats, you can get 1,000,000 FifaCoins, not redeemable for real money. Of course, you can certainly buy FifaCoins for real money.
A blockchain implementation could potentially allow people to sell that card directly to somebody else, for real money (or more specifically, crypto tokens that can be redeemed for real money). Would you rather have 1,000,000 FifaCoins, or $100?
Whether or not this is desirable to games is a different question, but the game is already essentially pay-to-win, so it's not like it would ruin the game from that perspective. It already has microtransactions. The main reason you probably won't be seeing this is because it would cut the publisher (EA) out of the loop, which is very, very lucrative for them.