Economic in real life

Why milk is in a square box to sell, while coke is installed in round bottle?
Almost all soft drinks, whether glass bottles or aluminum cans, are all in cylindrical containers. But milk box seem to be all square. Quadrate vessel can use shelf space more effective than cylindrical vessel. Why, then, soft drinks manufacturers insist to use cylindrical vessel?
One reason might be, soft drinks are mostly directly drink, so it is easier to hold them in hands with the cylindrical vessel even it brings extra storage cost. And milk is not so, most people will not directly drink milk with box . If milk containers is cylindrical, we need more big refrigerator.
But even if most people directly with box to drink milk, cost-benefit principle also shows that they are unlikely to pack in cylindrical container trafficking. Quadrate containers (no matter what) containers indeed can save shelf space, but milk case saving space, obviously more cost-effective than soft drinks. The most soft drinks is on the open shelves in supermarket, the open shelves are cheap, usually do not bring operating costs. But milk is required in freezer, which are very expensive, and the operation cost is high. Hence, freezer storage space is invaluable, thereby improving the  benefits of use square containers.