Last one. Why I'm doing this. I got into a discussion with a coworker about it.

Grammar checkers are great, but they don't look for stylistic issues. So reducing adverbs, detecting echo words ("she jumped on the jumper, jumping on his knee to shatter the bone"), my personal love affair with gerunds, or pointing out when I accidentally used present tense in my novel.

That's what AI is mainly for. To catch those things that an editor would catch.