Wheels and balls have also been found across the world.

Dodecahedrons are fundamental shapes. Thus universal. And also expected size would be pretty much same. In general symmetry is pleasant. So I would expect symmetric shapes to come up when people have enough time and resources to build them, even if they have no use.

Dodecahedrons with nobs on the vertices aren't really fundamental shapes. As far as I'm aware there have been zero found without the nobs on, and hundreds found with the nobs.

They are not symmetrical, though.