I am not an economist, but I assume that there are grain reserves so that prices don’t plummet when the supply goes up. If prices dropped too much, farmers would fail and we would all lose out since our food supply would be threatened. I think that the failed communist experiment has proven that without a profit motivator, people do not produce.
And by the way, when Yosef stored the grain for Pharaoh, he did not give it away to the hungry during the years of famine. They had to pay for it, and when they ran out of money, they traded their cattle and land, and then finally when nothing was left, they sold their own selves to Pharaoh, who then had to feed them since they were his property.