It stems from the original Mercurial implementation. The goal here is that every operation leaves the repository in a good state that can be pushed/pulled. That

It stems from the original Mercurial implementation. The goal here is that every operation leaves the repository in a good state that can be pushed/pulled. That's why Mercurial and Sapling rely on commit/amend/uncommit, etc and for example usually discourage the use of interactive rebasing in favor of restack and other operations that add another "state". It facilitates the mental model for developers without actually removing workflows (they are just different).