This question is very classic, and it was mentioned in the book "Milk and Coke Economics". I believe most people will have this question, why is milk sold in a square box, but Coke is sold in a round bottle? Here is an excerpt from the book for reference:
Almost all soft drink bottles, whether glass or aluminum, are cylindrical. But milk cartons seem to be square. Square containers use shelf space more economically than cylindrical containers. So why are soft drink makers sticking with cylindrical containers?
One reason may be that soft drinks are mostly consumed directly from the container, so the extra storage cost of the cylindrical container is offset by the fact that it fits better in the hand. This is not the case with milk. Most people don't drink milk directly from the box.
If the milk container is cylindrical, we need a bigger refrigerator
But even if most people drink milk directly from the box, the cost-benefit principle also shows that they are unlikely to be sold in cylindrical containers. Yes, square containers (regardless of what they contain) do save shelf space, but the space saved in the case of milk is clearly more cost-effective than in the case of soft drinks. Most soft drinks in supermarkets are stored on open shelves, which are cheap and usually have no operating costs. But milk needs to be specially packed in freezers, which are expensive and costly to operate. So, storage space in the freezer is at a premium, increasing the efficiency of using square containers for milk.
There are also many interesting classic cases in the book, which are common in daily life and will be helpful to friends who want to understand economics.
