For me, writing with pen and paper provides my brain a physical anchor point, a real idea stored in time and space. I find much more connection to my writings when I know where it exists in a physical space, and where I was in a physical space when I wrote it. Digital doesn’t have that anchor point for me, it just goes “up in the cloud”, far and away where the sprites and fairies live. My most profound personal growth happened because of writing with pen, being able to diagram and have the flexibility of 2d space on a paper rather than 1d ish space on a word processor. That doesn’t mean I keep everything written down on paper, though. Usually just journals.

Also I find that because writing is slower than the brain it forces me to summarize my thoughts into less words, reducing the informational complexity… making it succinct and understandable