As with the refrigerator, it took the milk carton two or three decades to catch on. People had become attached to their glass milk bottles.
Emotions be damned, here is the thing. Glass is heavy. The weight of the bottle makes up a total of a third of the weight of a unit of milk packaged in glass (yes, sometimes they still are!). Hey, and you know what? Hauling giant bricks of ice around to put into an icebox is a huge drag!