Rhetoric is communication designed to have a persuasive effect on its audience.
Here are some common rhetorical reasons for making diagrams and maps:
Jim owns a retail store. His profits and traffic have been declining for the last few years. His employees are convinced that, to save the business, the company website needs to let people buy things online. But all Jim sees is more complications, more people to manage, and more expenses. He thinks, "If we sell on the website, we have to take photos, and pack and ship each order. Who will do that?"
With rent going up and profits going down, Jim isn't sure if changing the website will save his business. He doesn't know the distance he needs to travel to get to his goal. He wonders, "Will improving my website even help? Or will it just make things worse?"
To think through this decision, Jim:
If Jim's goal is to increase in-store traffic and reduce expenses, an online store probably doesn't make as much sense as other things he could do.