alt Hacker NewsThe reason it's really bad to use nukes is that other parties with nukes will use them on you back.
And on top of that, many of those other weapons are also not used to avoid escalating? There are pretty high costs to using bioweapons even against non peer opponents.
Unless your simplistic game simulation says "I can win with a decisive first strike and they'll have nothing left."
Nuclear deterrence has been a mixed bag at best: https://www.amazon.com/Five-Myths-About-Nuclear-Weapons/