Folkiedave: because he told them not to. Often, and loudly. Obviously he did not set the police on them, or shoot them, but he brought whatever influence he could to bear on the situation to prevent people singing Rock Island Line and John Henry in the wrong accent. And he didnt want them trying to imitate the right accent either. I can see why he did it, and sympathise. And it was a good thing for English music that he did raise those questions: though I'm not sure that he wouldn't have been a bit more successful if he'd used a more softly softly approach.