Except they do, all the time.
They quit their failures. They don’t let irrelevant things like sunk costs, saving face, or unwillingness to admit defeat cloud their judgement.
Winners also quit while they’re ahead, when they’re already up the hill and the only way left to go is down.
Winners become winners because they quit things that need quitting.
So when should you quit a project and when should you persist? There’s a great discussion on that on the Tim Ferris Show.