In Kim Il-Sung's (the first of the Kims) time there was some sort of attempt at improving the lines of the North Koreans (as ineffectual as it was), but certainly in the reigns of his son Kim Jong-Il and his grandson Kim Jong-Un, it does look like power for the sake of power. I suspect at this point there is a fear (not just from Kim Jong-Un but also the higher ranks of the military and administration) that any sort of reform will lead to them not only losing power but also their lives.