The problem is the food you are storing is constantly going bad. So you need to recreate the entire massive food stockpile every year or so, in order to have it ready when the time comes. We'd have to find a way to efficiently cycle food through the stockpile and back to consumers before it became useless. But I doubt consumers are going to be lining up to buy old food. The food would be expensive to buy fresh, then wouldn't sell for much when it is old. It would be a crazy expensive program, and it would increase the price of fresh food for everyone.