Knowledge sharing is so tough to promote and make it happen because of 2 primary reasons - greed and fear.
We are all greedy for more. More money. More love. More that. More this. Apropos, some are greedy for more information and knowledge than others. They would love to take. But they don't want to give. Even if they give, they give the useless or maybe what they perceive to be useless. No knowledge.
We all fear certain things. Some fear animals. Some fear fire. Some fear death. Blah. Blah. Apropos, some fear that people will take away what's 'their's'; some fear they will not get what they give; some fear they will be taken advantage of; some fear being 'used'. So, they don't give knowledge.