Most agricultural policy or subsidy has purposes other than profit. A very strong evidence for this is that huge amounts of excess food are often disposed of very cheaply, e.g. by export to developing nations as foreign aid (wikipedia.org), or as part of local food bank or food stamp (wikipedia.org) programs. Agricultural economics (wikipedia.org) studies these 'other purposes' to see what insights they provide into economics, and to help set such policies in the context of a larger economy in which most activity is not agricultural.