I think it has more to do with licensing issues than techical ones. You have to remember that all the cars in GRID are race cars; I doubt the car manufacturers want to see that kind of damage being inflicted to their ordinary road cars.
Well I suppose but at the same time, Forza 2 has standard road cars also, with damage too. Now granted, Forza 2's cosmetic damage is (in my opinion) pretty terrible. I mean I played the game a fair bit but, it's a game where you have a 200mph head-on collision going round the track the wrong way and... your bumper falls off 👎
The point is though that the Forza devs get to damage these cars both visually and mechanically. I know it's a tired arguement to claim, "Oh well Forza has it!" but it does baffle me since they have a lot of the same manufacturers in both games. I'm not sure how each game compares when comparing which one has which car manufacturers but
if there were one or two car manufacturers refusing to allow their cars to be damaged, I really think Polyphony Digital would do well to just remove their cars from the game, and go for universal damage.
I mean, I'd rather have 800 cars with damage than 1000 cars with only 170 damage-enabled. It's a frustrating situation really since PD says one thing, but then there's Forza which has somehow managed it. As far as preferences go, I'll gladly take GT over Forza for a variety of reasons, but the next time Kazunori claims that some manufacturers don't allow damage, I'd really like to see an interviewer/journalist attempt to debate the subject with him by mentioning how Forza has managed to license it with no problems, and push for real answers.