That each new developer needs to learn that name. That it's difficult to understand what is that variable scope: does this new functionality fit in John or not.

That each new developer needs to learn that name. That it's difficult to understand what is that variable scope: does this new functionality fit in John or not. That most people know John but what happens with that other one that is rarely used named Jack and you find in in the code, and Anna and Maria? It would be the same for the computer running the code, the problem is for the developers trying to understand how to use it, how to expand it, etc.