North Korea is very skilled at manipulating world opinion to seem like a rogue state. They know very well that their existence depends on never taking action, no matter what they say.
Think of them like a crazy family member that keeps in trouble unless people pony up cash and you pretty much have their entire strategy in a nutshell.
Well, beyond that you have the fact that in order to maintain the kind of control that the regime maintains, they need isolation. This means that they do things to get isolated, so that the North Koreans get only one side of things.
As US News and World Report once commented, threatening the North Korean government with isolation was like threatening a drowning man with a life preserver.....
Think of them like a crazy family member that keeps in trouble unless people pony up cash and you pretty much have their entire strategy in a nutshell.