> Why in the world would you do squash merges?

Why would you not want to squash merges? It's one of three options offered by GitHub in their PR merge buttons.

They create a linear commit history, which is what you want when you have to audit changes.

> except to clean up messy mini-branches written by total noobs.

Nonsense. You get a messed up commit history as easily as when you create a PR in GitHub, and after team members merge their commits, you click on GitHub's "update branch" button.

You also get a messed up commit history if you merge a PR after someone else merged theirs.

You will always mess up your pristine commit history if you have more than one person posting and merging branches. With one notable exception: squashed commits.