3 ideas
Stripping an idea down to a single picture forces you to identify its essential structure, which exposes whether you actually understand it. The act of reduction is a test of comprehension: if you cannot draw it simply, you have not yet grasped what matters.
Abstract concepts become instantly graspable when mapped onto a familiar physical image — an iceberg for hidden depth, a bridge for connection, a funnel for filtering. The borrowed structure of the everyday object carries the logic of the abstract idea, so the viewer understands before they consciously analyze.
Forcing a complex idea into one small picture imposes a discipline that prose does not: you can only keep what is load-bearing. The frame's smallness is the mechanism — limited space eliminates qualifiers and decoration, leaving only the core relationship between elements.