My personal opinion is that we're so growth and value oriented - and that's fundamentally incompatible with a healthy diet.
Look at CostCo! They have an amazing amount of fresh, healthy meats and vegetables. But you're still walking out of that store with a twelve-pack of fish and the barrel of cheese puffs you saw on the way out. The majority of Americans simply lack the self control. The food production companies know this and take full advantage of it.