I tend to think of any substantial writing we do at work as an essay. Proposal, summary, RFC, employee evaluation, whatever. You can tell who writes well, and who is copy/pasting plausibly relevant text into an unedited draft that they then pass off as the final result. Not AI, just sloppy writing. I don't have numbers to back it, but I think that the good writing gets more done in less time. So, people care if you're good at writing essays.

Then there's the whole "clear writing is clear thinking" angle, but I suspect that people who write poorly do so out of laziness rather than any deficiency.