If you've ever been to Canada, you may have noticed something unusual about the way milk is offered at grocery stores. Milk may not always be found in a familiar carton or jug, but it may be found in a nine-pound transparent plastic bag.
Drinking milk from a bag is not a new phenomenon; in fact, Canadians have been doing it since the late 1960s. DuPont, a Canadian food and packaging firm, used glass bottles before introducing their thin, plastic milk bags in 1967.
Ultimately, all of those glass bottles weren't exactly cost-effective—and, once Canada switched to the metric system in 1970, it was considerably easier to comply with metric measurements in bag form than it was to build and produce new bottles and jugs. As a result, the plastic milk bag was born. Drinking milk from a bag is most common in Quebec, Ontario, and the Maritimes today.
According to estimates, 50% of the milk sold in Canada is sold in bags. Surprisingly, Canada isn't the only country where people drink milk from bags. Bagged milk is also widely available in India, China, Russia, and many other countries across the world.
Source: CBC