Didnt most tribal societies have a specialist system. a bowyer, a fletcher, a material gatherer etc. I would bet there was a master bowyer and others learned basics. Ishi made his own bows and arrows but I would think that was out of necessity being there were about 5 people in his group (not sure how many were found with him). maybe the hunters/warriors need to learn more techniques to be able to fix any issues while out on a hunt or during a long excursion of some sort... again no basis except speculation, correct me as needed!