Monty Don will probably agree with you because he doesn't use the stuff. Many of the rest of us dip hard or softwood cuttings into a bit of rooting compound to stimulate new root growth from 'above ground' cuttings. Depends on the plant though - have never had a problem with soft fruit cuttings or toms for example, but rosemary cuttings take quite a bit of 'getting going' and if I was wanting to propagate a lot I'd consider using rooting compound.
