No they don't (necessarily))??

Notice how they didn't spread the cookies evenly on the tray? If they had, it would've resulted in squares - not hexagons. On the left, some cookies look more like squares already.

Hexagons are just one possible way to tile the plane without gaps. The only reason bees use hexagons is because tiling a plane with hexagons results in the lowest possible total perimeter for equally sized shapes. And bees build the edges of their comb shapes using wax, which is expensive.