True, during times when I juggle multiple mature projects I find commits extremely handy since I can’t comfortably fit enough context.
But a lot of the time my work is a string of exploration and in-depth sizeable PoCs until something solid and worth documenting rigorously is born. I strongly feel that if I spend time writing up each change as a “green” atomic commit at earlier stages when things are routinely rewritten and rethought, I might never arrive at the latter stage in a satisfactory way.
During such intense work, commenting about my implementation is a radically smaller context jump for me than switching my mind into “commit mode”. This is likely individual: I tend to be overly perfectionist with commits, trying to never mix style and logic changes in one, to make sure a fully functional version of software can be built at any given point in history, etc.
From another angle, I think a lot can be achieved with other forms of documentation, which you mention and which should not be underused either. Of course, best is having your APIs, architecture and units properly documented. It is undeniably bad form to refer others or future yourself to comments, especially for why’s. However, it’s arguably even worse to direct them to commit messages (though in a team it could be an invaluable troubleshooting instrument, that is not the context I have in mind).
(I would never advocate “fat commit” approach to be applied to teamwork on larger projects. Just wouldn’t recommend taking commit count as an axiomatic measure applicable at all times.)