> Religion always seems like the default explanation for anything without an obvious use and it seems lazy.

This is one of the bits I remember from reading A Canticle for Leibowitz as a kid. It's about monks in a post nuclear armageddon world. At one point they find an ancient fallout shelter with a bathroom, and they interpret it as a spiritual space where a priest would sit on the "throne" and read "holy scrolls" held by the metal bar next to the throne...

I think we make that kind of mistake when doing armchair archeology or anthropology a lot.