You teach what you know best, maybe you teach your niche. And you only need that 1 guy who come along and do better than you.

The Japanese were asked why they taught the Koreans to make cars. Their answer was that if they didn't do it, someone else would and they would control the Korean industry. Fast forward many years, the Koreans are encroaching on the Japanese last niche of luxury cars. In hindsight it would have been far better for the Japanese do nothing. The Korean auto industry would have been delayed and then for better to let the French, British or Italian teach them poor engineering. I read about what the Japanese thought in the beginning, did it in my business and regret it the same now.