Cheaper Than a Cylinder

A single bee cell could be a circle, which uses the least wall for its area. But circles packed together leave wasted gaps, and gaps mean more total wax for the same storage. The hexagon is the next best thing: it keeps almost all of a circle's efficiency while sharing every wall with a neighbor.

That shared-wall trick is the real saving. Each wall does double duty, serving two cells at once, so the colony spends roughly half the wax it would on separate round pots. Wax is expensive to make — bees eat several kilograms of honey to produce one kilogram of it — so every gram saved is honey kept.