I remember milk and yogurt(drinkable kind) in bags from when I was a kid living in Argentina. Everyone's house always had 2 plastic holders to put the mil or yogurt bag in them.
I believe some stores had small milk crates, where 9 bags or so are placed into and then they sit on the cooler shelves. Customers just grabbed the bags from he crates.
All the labeling and "regulations" of eggs, chickens and cows are all bullshit. My wifes brother-in-law has a small cow farm(for beef) and is looking into getting into chickens as well. It's really all crap just to get people to pay more for basically the same crap it always has been. Whats the worst is that its what the people initially wanted but since we have to feed sooooo many people, the regulations are SUPER lax so as to be able to call something one thing and that thing barely qualifies for it. He says in some ways it is way worse.
So for eggs, he pretty much says to raise a couple chickens so you can have your own eggs or just buy the cheap stuff. There really isn't any real difference other than the price.