The main selling point for me was the "zoom in/out" aspect. Instead of having a HUGE UML diagram, you have a bunch of small diagrams, each focused on a single part of the described system and the interactions between its components.
But for level 3, 4 it gets tedious to do the diagrams at time and harder to keep them updated over time. Personally I prefer to just read the code and only have diagrams in special cases at this point
You can version your diagrams with your code (or in their own repo) using PlantUML, and by following the C4 Model you create digestible diagrams that are easy to understand.