Honestly? The most likely scenario is that a very large asteroid is spotted heading for earth some decades or centuries in the future, and we have to use every

Honestly? The most likely scenario is that a very large asteroid is spotted heading for earth some decades or centuries in the future, and we have to use every warhead we have to blow it up or turn it away. Extremely unlikely, but still more likely than humanity voluntarily giving up all nuclear weapons. And some people will build more. Always. The knowledge is out there now, and people will build them for a power trip or even just shits and giggles.