It's the same outcome either way. You don't have nukes and another country decides to nuke you? Your country doesn't exist anymore! You do have nukes and another country decides to nukes you? Your country doesn't exist anymore! What changes?

People say deterrence, but what is the deterrence? You built something that you'll never use? What's the point?? Oh you will use it? Great! You've decided there's some event that is so bad you'd end the world if it happened. I'm not sure what event that is. Maybe you have one in mind? China attacks India? The world should surely be destroyed then! No? Too bad! You don't get a say! China and India decide if humanity gets to continue! They definitely wouldn't do that though.

They built their nukes to never use them. Which is the same as not having nukes, but having nukes is required so that nobody uses them, which is the same as never building them, but they need to be built so they won't be used!