We usually stick with squares or rectangles when we're building things, with right angles everywhere. The shapes tessellate - they fit together without leaving any gaps, like in an M.C. Escher drawing.
If we built with hexagons, though, like bees build their hives, we'd use less stuff and have more interior space. Unfortunately, we're not as smart as bees. Or M.C. Escher.
But if you buy a bunch of these shirts featuring this fascinating design by artist Eldar Gousseinov and fit them all together, you'll make one of us feel much smarter.