I may have already missed the window where people will read this reply, but let me tell you the basic error in your thinking. Yes it's true that Old MacDonald actually does exist. He may be your neighbor. He's certainly my father's neighbor, out in the country, in Michigan. And you can buy eggs. And a few other people, too.

But guess what. Well into the 90s percent of people don't do that. Probably high 90s percent. And they never could either, because as soon as they tried, you'd see it can't scale up. The only thing that can scale up is the rotten situation we currently have--the one that produces that 90s percentage of the eggs and milk (and meat, which you didn't mention, but it's likewise a parallel here for people who believe in "humane" meat).