system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If Hexagons are so efficient as a shape. Why are they not more commonly used?
gpt
There are many reasons for using the shapes we do... but one of the big reasons is that hexagons only stack well with other hexagons of the exact same size. Contrast this with squares and rectangles, which a bunch of non-uniform sizes can still pack well.

Also the lines between hexagons aren't straight, while the lines between rectangles are.

Last, rectangles generalize to three dimensions and remain stackable, while hexagons do not.