While I'm sure they're are good academic arguments around why null is not a great language feature, I think the simplest way to explain the problem is to point to the number of bugs, incidents, outages, failures, that all seem to be related to it. Billions of dollars have been lost to null.

You cannot ask for perfect programmers who will never slip up. We're humans. People make mistakes, forget to check for null. So why not instead just make these kinds of issues impossible? Let the build process look for the mistake and block you from making it.