It is the most efficient shape for packing/stacking. It provides the most area for a given perimeter. Bees use it:
These are made by living things of course, but perhaps there's a similar physical reason why this shape is occurring.
Also, if you put 7 soap bubbles on a surface, 6 surrounding a 7th, they form a near perfect hexagon. It's a VERY natural shape.
Sorry to bust your love-fest with the hexagon D-Fendr, the circle provides the largest area for a given perimeter.
Also I don't think it can beat a cube for ease of stacking... With hexagon tubes you can never pack to the edge of the container regardless of the side of the hexagon.
However, you are correct, bees do use it ;-)