Agriculture is strategic to a country, I would say like military is. And you don't let strategic market in the hands of international trade agreements.
It can be argued that any industry is strategic to a country.
And it's funny you should mention military, I know serveral companies in Denmark that are sub-contractors to various branches of foreign, including the US, military. Countries do indeed let the international free market supply their militaries..
True, but we still don't have enough independence yet (in France). If Agriculture were really seen as the strategic asset it actually is, we could instantly stop importations without starving.