A use case that interests me is dynamic visualization for debugging, when there are interacting systems.

To flesh this out, let me see the volume of calls and data from one place to another. Help diagnose back-pressure, drops, rejections, and any other irregularities.

Think of an on-caller who wants to quickly pinpoint a problem. Visualization could help one understand the nature of the problem before reading the code. Then you could select a part of the visualization and ask the computer to tell you what that part does, if there are any recent changes to it, etc.