Pretty sure it’s mostly an American thing, but I’m not well-travelled enough to be sure.

And as for rate of consumption… When I was a kid, my parents made me drink a glass of milk every day - call that 8oz, so 56oz per week. That’s a little under a half gallon (which you can also buy in plastic jugs), not including other uses like tea/coffee and cereal. Altogether, we’d go through about a gallon per week.