What makes a horse more eligible for a bit-less bridle/hackamore than a bridle with a it?
all horses are different and a good trainer will evaluate the horse to see which method would bring out the best in the horse that is being trained.sometimes it is neccesary to use a hackamore or brockamore due to mouth problems but some horses wont respond to them and need a bit.the old way of training is using a progression of bits and hacks in order to refine a horse but a lot of trainers dont use the progression and want to skip steps or they are just not educated enough or have rough hands so they compensate with a bit.a lot of cowboys will just use a halter and a set of reins or a lead rope to train a horse for neck reining and the belief is that without the trust of both the rider and the horse working as one you will spend more time fighting with each other than doing the work.its not natural horsemanship , it is just good common sense.
