Rhetoric matters.

Rhetoric is communication designed to have a persuasive effect on its audience.

Here are some common rhetorical reasons for making diagrams and maps:

Reflection: Point to a future problem (e.g., a map of a local landfill’s size in the past, present, and projected future).
Options: Show something as it could be (e.g., a diagram showing paths a user could take to set up an application).
Improvements: Show something as it should be (e.g., a diagram pointing out opportunities found during user research).
Identification: Show something as it once was or is today (e.g., a map of your neighborhood).
Plan: Show something as it will be (e.g., a map of your neighborhood with bike lanes).

How to Make Sense of Any Mess by Abby Covert