What is this? 1656 Japan?
Well, no, but people in some arts actually compete in martial arts tournaments, etc., and while it's not as life-threatening in a tournament as it was in feudal Japan, you still don't want to rush out and give away all your knowledge/skills if they're giving you an advantage, right? I.e., there's nothing wrong with people being careful not to give away their knowledge and skills to every Tom, Dick, and Harry who demands it.
Besides, a lot of Aikido people are in this I.S. pickle simply because Ueshiba didn't teach the skills openly... and he's not from 1656 Japan.