The problem that Greg is referring to here is that `git commit` (as for many other version control systems) overloads two distinct operations: checkpointing your work and creating a new revision. Forcing you to provide messages for the former use case can even be counterproductive [1].
Contrast this with, say, Smalltalk's ENVY: saving a method automatically versioned the method (without the need of providing any other metadata), but you could also separately create system snapshots as named versions.
Common Git usage is to squash checkpoint commits, anyway, with individual commit messages often disappearing in the process.