I don't understand the point of variables if they won't work.

Phil is correct.  When returning to a slide, you have three options; to return to the saved condition, to return to the initial condition, or to allow SL to decide which condition (automatic).  So to Dan’s point, none of it is intuitive, all of it is by designer choice.

Initial changes everything back to its original position, and the slides runs everything again. Variables are not returned to their original values because they are not objects on the slide. They are post-it notes that are impartial, outside observers of all that is going on, and carry little bits of information from one part of the project to another. As such, they can be changed only by triggers, not by returning to the slide.

Saved leaves everything on the slide as it was when you left it, except for variables and the notification that the timeline is starting. Strangely enough, returning to the saved condition doesn’t re-run anything. It just announces that the timeline has started again. That means that any trigger that fires when the timeline starts will fire again, but objects that have changed state will be in the changed state, and triggers that depend on time cues don’t fire.  See the attached file.

Automatic (as Phil says) is the worst of all possible options, because you don’t have any control over it, and it isn’t really predictable. It decides which condition to return to, based on unknown factors.