When you only grow stupid barely edible shit like corn and soybeans, the next logical step is to build a shed and feed a thousand pigs the corn and soy.
I was exaggerating, but the majority of corn and soy grown go into non human consumption or highly processed human food. 70% of American soybeans are used for animal feed. Mostly chickens in America and most of the exported soybeans are fed to pigs in China. 5% is biofuel. That's 75% of the crop not being for human consumption. And of the 25% left who is used for human food, 80% is used to make cooking oil.
It's a similar story for corn. 45% is used to make ethanol even though without government mandating it be added to petrol, no one would. Then 40% is fed to animals. That's 85% of corn that was grown not for human consumption.