The reason Gran Tursimo’s developers gave, right from day one, for why there was no damage to the cars in their game, was that manufacturers would not allow it. Mathew isn’t guessing on that one, they actually straightup told magazines that’s why no damage occurs.
Are they lying? Doubtful - I think it’s more likely that because the game was sold as hyper realistic, the manufacturers revisited how they felt about games showing their cars broken, and decided for that series it was a no-go.