I think we on this forum forget that some people aren't as horse smart or experienced as we are. I know some trainers that know how to ride but have no clue about horse personalities. I am amazed by the number of people who've ridden for years that don't do natural horsemanship yet can't even lunge their horse or roundpen it properly. So I think Parelli(and other popular trainers)are helpful with groundwork and horse sense. Because it's not all about riding. It's about horsemanship on the ground too.