Another insidious motive for the avoidance of writing: keeping things off the record.

Writing requires you to put your name on your ideas. It promotes other pro-social traits, like being vulnerable. It's a lot harder to do negative politics if you're required to take your claims to paper. It's a lot harder to spread misinformation if you have other folks in the organization that can easily go look up your claims and fact check them.

Taking everything "offline" is a great way to bully, lie, cheat, and steal without fear of accountability. It hides incompetence. Weak leaders avoid writing lest they be exposed.