Its just "old" thats all. More importantly no one knows how to make any new content for it - i.e. add-ons. Its only natural to become bored with the original product after so many years.. you cant get anything new out of it by playing it.
I still play it though, but then again, im a freak.
I would love we could figure out how to create add-on cars for the game. the only other game I play religiously is carmageddon 2 and I like making cars for that game. Too bad those damn people who made it never told anyone how to do anything like other games.
Too bad driver2 wasnt made for PC to, what the hell is up with that?