Why Milk Comes in Bags in Parts of Canada.In parts of Canada—like Ontario, Quebec, and the Maritimes—milk often comes in plastic bags, a packaging choice that dates back to the late 1960s. A Practical Shift
Before 1967, Canadians bought milk in glass bottles, which were heavy and costly. When plastic bags arrived, they were lighter, cheaper, and easier to transport. The switch became even more appealing in 1970, when Canada adopted the metric system—bags easily adapted to new volumes, unlike rigid glass containers.