I find I write for two reasons:
To communicate with someone
To process my thoughts
When communicating with another person, it is considerate to be concise.
Whereas my own thoughts may ramble across the page like partially broken wheels spinning off on multiple tangents; following them all to a logical end is unlikely, expecting others to parse out their meaning is impudent, almost. Their value is in the process of penning them down - to capture the fluttering ideas and inchoate thoughts with an excess of detail and emotion as I experience them.
When I write for myself, it is to understand the puzzle.
When I write for others, I must first assemble a picture from the pieces.
To spill ink onto the page with reckless abandon feels like committing a crime against the reader - a grave sin that I must avoid, their time is valuable and their attention limited. Have I pained them their time for no purpose? Was there any value or meaning in the conveying of my message? These doubts are not for the reader to wallow in - they are my responsibility to understand before sharing my writing and thoughts. I must stand my ground so that the reader can use my writing as a sounding board, a perspective to consider or argue, a fixed point from which they may see new light.
There is beauty in the pith and meaning in the spaces.