The problem is EA treats it like every other sports game. You can get away with releasing a new football or basketball title every year because there's enough change to warrant it. In the last 10 years though, EA has released at least 14 NASCAR titles, more if you count arcade. So there's some over saturation there. And then you have the problem with the games simply not being as good as they used to be. NASCAR games used to be challenging and engaging. Now they are pretty dumbed down in the gameplay department and full of over the top presentation.
If they moved to a 2 year cycle and had strong post-release support for the games with DLC and all, I think it would make a huge difference to their sales. But then again maybe the NASCAR license just wasn't worth the money, kind of like 2K Sports is finding out about baseball. And maybe they see what companies like Polyphony are doing and figure why bother. They can't compete with a Gran Turismo.