User blog comment:KingWizard/Think about it/@comment-11437688-20130713120246

It was said in the novels that the reason they are not sharing the tech to the outside world is to control the Kiharas:

“But if that concentration in Academy City is destroyed and science is scattered throughout the world, Kiharas will naturally start cropping up all over the world. They are currently bound to a single bloodline, but that is not a necessity. If you Anti-Academy City Science Guardians expand, the world will be overrun by Kiharas along with the technology. Academy City will be unable to control that.”

Also:

 " When people wish to misuse a field of pure science, someone appears to actually do it. That is what a Kihara is."