First of all I'm an eventer through and through so this is more out of curiosity than anything. I don't know much about how most people ride/train in the Hunter world.
Anyway, there's a girl at my barn who started riding hunter and has her own coach come in to give her lessons. I've been riding at the same time as her a few times and saw that her coach makes her ride with regular reins, draw reins, and a standing martingale. To me it seems really odd to use draw reins with a standing martingale, and jump with the draw reins on. Usually I only use them to teach a horse how to go in a dressage frame if it isn't quite getting it.
Is it common to work in draw reins and a martingale at the same time? And jump in them? What does this accomplish?