why bother trying to describe something that doesn't happen?

It's easier (and clearer) than describing exhaustively all the things that do happen and not including that which you specifically wish to say does *not happen. In terms of an idiolect you may wish to say that you never ever ever use the word f**k without having to list all the vulgar terms you would use.


In terms of the software example, if you don't care whether there is a value left in a certain variable you needn't mention it but if it is important to other parts of your program you may wish to specify that nothing be put there.