Ah passion, is it! I have a theory that the most successful folksingers are the ones with an intense singing style. This side of the pond, that would include Dick Gaughan, Martin Carthy and Paul Brady; And I think folkies respond to them because the majority of folkies are a product of the rock era, and have an appetite for "intense" vocal deliveries. "Lyrical" folksingers - Roy Harris and Cyril Tawney, for example - have never been as popular.