Originally posted by Eagle 
I hear CMR04 has a really cool damage model too. We covered the lack of that as well.
I doubt it's a memory issue with storing the cars on a memory card, you'd just need an indicative number that corresponded to a certain level of dirtyness, a certain number of layers of dirt by your example Travis.
Rendering dirt in real time, in a way that doesn't look cheesy and predictable, is something else. To actually do it with any degree of realism would take a lot of processing power, so I'm guessing that just like damage, KY has chosen all or nothing and wound up with nothing. Personally, I'd rather nothing than a half assed attempt.