The topolgy mapping is a nice feature to have but not strictly necessary imo. It shows in a more intuitive, vivid manner the same information about which modules are/aren't communicating as any other scanner would output in digital format.

Additionally it reveals instant information about which modules are supposed to be on the same bus/network. Nothing that couldn't be found in service information or a good wiring diagram.

In a professional environment with tons of diagnosis related to communication issues primarily it's a timesaver; the DIYer perspective may have different priorities.