[_delirium]

Animal consumption has scaled considerably faster than population, so I don't think it's solely that. The traditional Mediterranean diet, for example, uses much less meat than is now commonly consumed in the Mediterranean countries.

My guess is some mixture of affluence (can afford to import meat from faraway factory farms), the factory-ization itself (meat is a cheap-ish commodity), and decline in cooking skills and time available to use them (most good vegetable-heavy dishes take more time and skill to cook than a hamburger does).