This is a particularly ignorant and clueless opinion to have.
The whole point of Europe's common agricultural policy is to preserve the potential of agricultural production as a strategic asset. Europe's strong economy and huge population density, coupled with cheap access to agricultural production from south America and Africa, renders most agricultural activity economically unfeasible. The problem is that this means Europe is particularly vulnerable to a blockade, and in case of all out war the whole continent risks being starved in a few months.
The whole point of EU's common agricultural policy is to minimize this risk.
Owners of farmland are provided a incentive to keep their farms on standby even if they don't produce anything exactly to mitigate this risk. It would be more profitable to invest in some domains such as, say, real estate. Look at the Netherlands: they are experiencing a huge housing crisis and the whole land in Holland consists of dense urban housing bordered by farm land. It would be tempting for farmers to just cash out on real estate if they didn't had an economic upside.
You would do better if you educated yourself on a topic before commenting on it.