Milk is on a little island of drinkable things due to its perishability. Paper's a pain in the ass half the time but it's the most modular in your fridge. Jugs are convenient due to size but they're space hogs and bagged milk needs a whole shelf on the bottom to lie on and not get poked by something. And then glass, where let's face it, tastes fucking awesome, but break one of those in the middle of cooking breakfast and you'll lose your shit.