I never realized that how we purchase milk was viewed so peculiarly by those outside of Canada. We've always purchased milk in three bags totalling 4 litres. When one bag is finished it gets recycled and we drop another bag in the pitcher. Here are the steps involved for those unaware of what I'm talking about.
I suppose bagged milk would sound strange to someone who had only ever seen milk sold in cartons or jugs. After three decades of bagging it, I can't imagine buying milk in any other format.