[anaerobicover]

> it raises an interesting follow-up: why not squash and rebase entire months or years of project work into single commits?

That's effectively what happened before version control/before the small-scale rebases we enjoy now were possible. And the reason is that it's hugely valuable in certain circumstances to be able to see some granularity of the history. (Though clearly people disagree about what the grain size should be.)

> Could we read and understand massive projects quickly and easily, if they only had a few commits to them?

I don't think so. The current state is visible at the top of the git tree regardless. History comes in when you are trying to understand why the state is what it is. Usually this is for troubleshooting in my experience, but sometimes also when doing a refactor. Meaningful commit messages attached to meaningfully-clumped patches are, in my opinion, absolute gold in those cases.