Perhaps it is a case of WHERE said nuclear weapons are. If they are in a stable government with little chance of them being used (US, EU etc) then they are only used as a deterrent to war.
If however those nuclear weapons are in an unstable country with enemies known to be nearby (Iraq/Iran, N/S. Korea etc.) then it can get a little tense and may be used without prior thought or reason
Who determines stable governments?
"As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality." - Albert Einstein