It easily bridges over sections of code and documentation that are otherwise tedious to produce. I can just write a dense rambling explanation, and it'll decompress that into a piece of text or code that includes all the well-known bits that I skipped in my description.

Also fun is just to write out a hypothetical library idea, and walk through a whole hypothetical development process to validate it, steer it in alternative directions, and find the more challenging points for improvement.