The fact of the matter is.. none of us know the real reason. SMS are under very strict NDA from both Microsoft and Sony (it's something all developers who target consoles have to deal with).
I'm more frustrated that none of this was possible to predict earlier and just shift the damn game a whole year, like Driveclub did, back in 2014 when the first real delay happened.. just to be on the "safe" side. Now there is potential for these tiny "2 weeks 1 month" delays happening frequently and really gnawing at the patience of everybody. Oh well.. we'll see what happens. It'll be out when it'll be out.
.. and it's easy for me to not be too disheartened as I have the luxury of playing pCars at any time I want. I thank myself for being smart at least once in my life.. for investing early into the project!