Because I feel better when I don't eat grains. Mainly my intestinal tract is in better condition (though I don't have coeliac disease), but there are other benefits as well. Besides, restricting my grain consumption is the only way I've ever been able to lose weight. Low-carb diet is the only diet I can actually stay on, even though the beginning is hell. But once the cravings pass, I can actually lose weight without feeling hungry at all.