It can indeed add more "pop", but in many cases, learners do not have the skill to manipulate the lead line, at a disance, without applying too much umph to the rope and popping the horse too much under the jaw. Then, one goes right past the spot with the soft feel and straight into a very strong bop on the underside of the jaw. hard for beginners to find the place that is getting the message across wiht the littlest amount possible. Some horse's get fearful of that bop under the jaw and end up throwing their heads up even more .
however, it's not a huge deal either way.