What some people don't seem to understand is that is a racing game, not a driving game. The focus is on the career and the progression into the higher echelons of racing. They could have had (at one point they did) have all fictional car manufacturers, and the game would have been the same.
Not buying this game just because it doesn't have your favourite brand (which in a motorsport setting, doesn't have a great many cars to choose from, apart from a few variants on Corvette or Camaro GT cars) is madness, because you just won't realise what you're missing. I'd rather forego my favourite car (the Dodge Viper) to have a game that plays as well as this does, the controls as well as this does, that has the online capabilities in terms of playing and league organisation that this game does, than have a few more cars that doesn't make any sense in the structure of the game.