Because they don't -want- people to know what they have, Justin. It gives them an edge. These arts have often been kept as family secrets, not public knowledge. Their existance has most probably gotten out into the Western world by accident, not because the Asian possessors of those skills wanted to "share them" with the world.
We figured out in the computer world security though obscurity does not work. Too bad the rest of the world has not caught up.