Keeping a group's training methods secret is one thing. What I am really wondering about is more along the lines of parallel evolution, or accidental discovery. Why did just one group discover and develop these concepts, disseminating the ideas to a pretty small part of the world? Why doesn't someone occasionally, accidentally, and perfectly casually drop some epic touch of death on someone else? Why didn't Fluellen working in the fields of Wales discover a better way to push a sheep out of the leek patch?
different philosophy between east and west. the west adapts the environment to human needs. the east adapts human needs to the environment. the west built and created things to make life easier to live. the east tried to live with the environment. when east met west, the east adapted western technology and some of the philosophy; however, at the core, especially to martial artists or arts that spanned generations, the eastern philosophy still held at its core. my aikido teacher also does kyudo. he has two bows. one made out of fiber glass composite material and one made out of bamboo. as the advance in technology progress, the fiber glass bow can be mass produced which would make the bamboo bow making obsolete. fewer folks as year go by know how to make bow out of bamboo. then you got to ask, why would one want to study and use bow, when a gun is much better as a projectile weapon? same goes with sword making in modern technology age. the old ways are tedious and time consumming and so many way to mess up. same goes with IP/IS training. it tedious and time consumming and so many way to do thing wrong.
you know who else also good as keeping secrets? your grandma and/or your mom. there are cooking recipes that they won't tell folks, not even their own children or grand children. or they might told you about it, but you weren't interested in cooking so you don't care and end up not knowing.