The fact that its not very useful for the forms of writing most people participate in nowadays--short form responses that are heavily contextual. Even longer form writing is often labored over--people use LLMs for outdated types of communication, like long-winded emails or school papers.

Idk, working in the AI space, I've started to write very succinctly and straight to the point, maybe as a counterweight to the often overly flattering, verbose forms of prose that the LLMs employ. I pay close attention to every word and try to never write more than is necessary.