Written communication is inherently significantly more complicated. To "jot down" any idea you need to consider how that record will further be shared with others. If I were to write an .md file with a bunch of terms that only the 6 of us know what that's all about, then make a bunch of assumptions based on that. All it takes is one of the team members who doesn't agree to forward that written record to a management person then adding their own context (which I never got to add my own context) and get the whole thing vetoed from a much high authority than I care to argue with.
In a written communication, I need to elaborate and explain every single thing to everyone regardless of their knowledge level. Then add links to those who don't know. Then add links to the link to those who don't know. Then eventually schedule a meeting to discuss the proposal. then a meeting to discuss the results of discussing the discussion of the proposal.