Why indeed? For a nation, the benefit of having a nuclear weapon comes from not using it.
Why does North Korea develop nuclear bombs and rockets to deliver them when its people are hungry? Why Israel? Why did South Africa initiate a nuclear bomb program that it subsequently abandoned? Why Iran?
At present, nine nations have nuclear weapons, that is, a nuclear explosive sufficiently compact that it can be moved and delivered somehow. The U.S., Russia, England, China, France, Israel, India, Pakistan, and North Korea have nukes. Threatened by Soviet expansion in the 1940’s, the U.S. and its allies embarked upon a nuclear arms race with Russia. Russia participated in the race, feeling the capitalist market and free information threatened its communist beliefs. The resulting fragile peace became based on mutual assured destruction (MAD). India and Pakistan did likewise with each other. Without nuclear competition, Israel wanted military superiority over neighbors who were themselves committed to the termination of Israel, a first-strike defense that would be valid until a hostile neighbor develops a nuke. But why would an unthreatened country (North Korea, South Africa) invest wealth to develop a weapon of mass destruction?
Reason 1: Big boys at the table.
If you have a nuke, other countries will negotiate with you. Before the threat of nuclear delivery, did the U.S. negotiate with North Korea or simply attempt to contain it? Before rockets, did the U.S. talk with “little rocket man?” I once imagined a world in which we gave every country two small nukes, each one seeded with tracers to mark the cloud if it exploded, thereby revealing the perpetrator. All armed with a nuclear sword, everybody had a ploace at the negotiating table. But my scheme proved to be a bad idea in a world of irrational governments and rational terrorists. Furthermore, the terrorists might not need a nuke. Right now the score in the Middle East looks like Governments: zero; Terrorists: about five.
Reason 2: Susceptibility to fear and fakery.
Small nations and dictators want nukes in part because the U.S. has nuclear paranoia. So much so that for fifty years Congress has not approved any scheme for treatment or disposal of wastes from civilian nuclear power. Just the term “nuclear” causes us to jump. We label the medical photograph as “magnetic resonance image” (MRI) rather than to use the physical name “nuclear magnetic resonance.” Furthermore, fake news based on fear spreads, affecting governments. Consider the anti-vaccination and anti-climate movements. To affect American politics and policy, foreign governments can combine the paranoia with the social media.
Thus, the U.S. can be threatened by any dictator who has nuke, whether or not it he has many or his nukes are big. Likewise, a psychological epidemic can be triggered by a terrorist who delivers a small crude nuke by truck or bicycle. Remember, wars are still in progress that were triggered by four plane crashes on 9/11/2001. On 1-13-2018 the state of Hawaii generated panic when it accidentally notified every cell phone that a missile was incoming. Americans do not panic at 35,000 traffic deaths per year, but we do panic at the expectation of one potential nuke. No matter what your armaments are, you are not defended against a threat developed through Facebook.
So what can we do?
Slow down. Talk to other countries. Understand their point of view. Live down our image of sending in the marines when local responses threaten our foreign commercial markets. Regard terror against one is terror against all. Promote that regard world-wide.
Finally, recognize paranoia where it occurs, even paranoia regarding the opposing political party, and get over it.