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Nuclear weapons have limited usage due to arms control method of cooperation.
Arms control regulates the acquisition or development of weapons. The Anti-ballistic Missile (ABM) Treaty in 1972 tried to stop the United States and the Soviet Union from using ballistic missiles as a defensive shield to launch a nuclear attack. While it did allow both countries to deploy a limited number of defensive systems, it stopped them from large scale production of those systems.
The Nuclear Non-Proliferation Treaty (NPT) of 1968 was an arms control treaty in the sense that it regulated the acquisition of nuclear weapons: those countries that had tested and manufactured nuclear weapons before 1967 were allowed to keep their weapons; and those that had not done so were to give up the right to acquire them. The NPT did not abolish nuclear weapons; rather, it limited the number of countries that could have them.