So the manufacturers can make more money out of every box. It's not about the consumers, it's always about money.
Cereal boxes are not shaped to give greatest ratio of volume to surface area so that the manufacturers make more profit in less goods.
Cereal boxes are designed for practical reasons such as storage efficiency, manufacturing cost, consumer handling, and branding visibility rather than maximizing the surface area to volume ratio. The rectangular shape helps in stacking and reduces production expenses, making it the preferred choice for manufacturers. Although a sphere has the best ratio, it is less practical for consumer use and display.
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