> But, if your problem is simple enough that you can represent it with a handful of states with two or three transitions each, then you have a very trivial problem, so trivial that the state-machine diagram likely added nothing at all to your understanding of it.

And yet, it's extremely common to see apps with clearly broken states and state transitions for what should be relatively "trivial" state machines. Think play/pause buttons, buttons with loading states, form fields with error states, etc.