The plumber, the roofer and the electrician sell us a cure. They come to our house, fix the problem, and leave.
The consultant, the doctor (often) and the politician sell us the narrative. They don't always change things, but they give us a story, a way to think about what's happening. Often, that story helps us fix our problems on our own.
The best parents, of course, are in the story business. Teachers and bosses, too.