Stopping them two steps from stabbing range is very handy, because it means they never get to stab you. Even if you hit their shield, you'll quite probably penetrate and wound them through the thing. Should that fail, the big heavy iron bar sticking out of the shield will render it too awkward for use. You, still in possession of a shield, now have a substantial advantage.
Either that, or you throw the thing from horseback, in which case against somebody with a sword, two steps from stabbing distance is really quite safe.