It was a different era, a time when your skills were all that stood between you and rampaging warlords, bandits and even government troops stealing all you had, forcing you into joining their bands or death. We don't face these any more in a lawful society. Human life is valued more highly now and very few instructors would want to teach someone who claims they wish to know how to kill. Don't idolise death, life isn't a playstation game or die hard movie.
There's only one reason to need to know killing moves and thats to avoid them. ie if you are being taught a strike the instructor needs to let you know if you hit a particular part of the body it could lead to death so you would know to avoid that.