Aside from the obvious allure that nuclear weapons possess to dictators such as Saddam Hussein and the Kim dynasty in North Korea, they can serve as a mandate and a bargaining chip. In the case of Saddam Hussein in Iraq, even the slightest notion that a re-start of the Iraqi nuclear weapons program played into the strongman image that he cultivated throughout his time in power. It was so important that he continued to leave the question unanswered as the United States and its allies threatened invasion in the leadup to the Iraq War for non-compliance with international observers. By refusing to provide the proof that would save Iraq from invasion, he continued to act as if he had something to hide and feed into his strongman persona.
Similarly, it is not entirely the possession of nuclear weapons outright that drives the Kim dynasty to continue to foster a nuclear program. Having nuclear weapons gives North Korea a better negotiating position with the international community. Claiming to scale back (but not completely dismantle) its nuclear program can be exchanged for sorely-needed sanctions relief.
Ron,
Well, if that is how the North sees nuclear weapons–ie., as a bargaining chip–then you might have expected that they would already have struck a deal. It is more likely at this point that they see them as a way to prevent their ruling elite (the Kim family) from being overthrown. Unfortunately, I do not see a viable route to the North voluntarily giving up its weapons through negotiation as long as the Kim family remains in power.
–Professor Wallerstein