Because in the game it's for it actually does something.
>How would that even work?
They would need to come up with some kind of standard.
>Need for speed and Forza for example have dramatically different driving models.
You would want to standardize on one to try and keep things consistent.
>Does sharing stats between those even make sense?
Having the car you paid for be separate from the simulator you use to drive it makes sense.
>What about licensing deals?
Whoever is selling you the car NFT would license it instead of the game.