[Guidii]

So there are a few reasons to favour hexagons (or triangles) over squares....

Squares don't pack as closely as hexes, meaning that you can get 18% more hexes into a space than squares for a given perimeter-size. Squares also degenerate badly over the surface of the sphere.... you can't keep a consistent size as you change latitude, and they turn into triangles when you reach the poles.

[timmaxw]

Google S2 (a square-based alternative to Uber's H3) works by projecting the surface of the sphere onto the surface of a cube, then subdividing each face of the cube. So there's still some distortion around the edges and corners of the cube, but nowhere near as bad as a naive longitude/latitude strategy.