Part of the background is that the government wants to keep farmers “on hand” even when demand isn’t there, for national security reasons.

Essentially they want to be able to get more crops out of all farmers in a bad year, rather than rely on only a fewer number of farmers in a good year.

There are many greed/corruption/waste issues with this system, but all nations have a strong interest in keeping their breadbasket staffed up for hypothetical bad times