Trends in agriculture are driven heavily by cost. This is where the vegan fundamentalists go wrong, arguing that meat is "more expensive". But in the days before modern agriculture, people raised animals and had meat - it was economically beneficial to do so, even for people living at the edge of famine.

Cornfed beef is a result of economics, too - it's cheaper to buy corn than use pasture, and/or it produces meat that can sell for higher prices. We don't just see corfed beef for fancy prime steaks. It's used in cheap fast food hamburgers as well.

Fast food and junk food are the cheapest food. They've applied industrial logic to every link in the food chain. If meat was as expensive as vegans argue, we wouldn't see it as the basis of so much fast food.