If i hated xbox why do i own one? If i hated forza why do i own forza 4, and why have i played quite a few hours of the damn game? The problem here isn't me, it's you. If anyone says anything that isn't the equivalent of being a blind fanboy of microsoft you think they're on some kind of anti-microsoft hate parade. You really need to wake up and realize that there are people out there who aren't blind and ignorant fanboys like yourself. That there are people out there who don't blindly worship the god damn company you love so much.
Anyway, on topic. Perfect conditions at all times IS unrealistic. It has nothing to do about seeking out rain or snow or whatever. It's the simple fact that everyday and every race isn't going to be like a day in paradise.
But this isn't the real world. and most races do happen on dry surfaces. and lets face it, people would only pick rainy tracks to show off the rain effect or to have fun sliding around, not for serious racing which is what Forza is all about.