I’m just guessing, but I assume that after a certain point, what you’re trying to draw is so niche and/or new that no one’s bothered to make decent software for it. Like, you can do a Feynman diagram quickly on a chalk board, or spend 3x as long dragging lines in Visio or something to make a diagram diagram.

Even with CAD existing, I still always sketch initial project ideas out on paper just cause it’s fast and easy.