21% of Americans are functionally illiterate. 54% of Americans read below a 6th grade level.

Things that seem trivial to someone well-read can be insurmountable tasks for millions of people.

Those people may do fine day to day, you don't need to write all that many emails for many if not most jobs, but when they do need to get their intentions across, things might get dicy.

Or course this solution is far from perfect. If you use LLMs to word your message because you're not very proficient in reading or writing, you may not understand what the output is saying, so you can't verify that it didn't misinterpret you.