Earlier quoted context omitted.
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…
You have to be able to write enough to prompt an LLM. So why not just send the prompt, since that's what you actually said?
Back when I did customer support, I occasionally dealt with people who lacked the capability to express themselves in written language. These weren't people born in other countries or people with some kind of intellectual disability, often they were just never taught how to read/write/compose a message.
There's also a social stigma to sending a job application written like "good. morning. sir i. wnt too. Wrk for ur Compny u. hve job. for Me im steven i.m" and so on, even if the job in question has nothing to do with any form of written communication.
Plus, there are plenty of things people just don't know how to do. I once had to Google "how do I write a letter of resignation" and Google will now generate a fulll message for you if you type "i want quit next month how write".
I think the author of this blog post assuming a prompt to help improve a message (obnoxious glowing button aside) somehow implies that Google thinks they're stupid showcases the perceived link between the ability to write and intelligence.
Obviously, using LLMs for this is just patching over the lack of resources put into (adult) education and literacy, as well as a societal shift to stop treating illiterate people badly. However, structural improvements take many years, probably several rounds of elections, and doesn't help someone today.