I think it is anyone who wanna make sure they write correctly. I know for example David Sparks (MacSparky https://www.macsparky.com ) uses it (or at leased used it). And he was an American lawyer and he says writing has been his passion his whole life so I assume his English is better than the average person.

I use it as a proofreader, not to improve my writing. It’s difficult to proofread your own work, and Grammarly is a useful assistant. Plus, I’m British and I often write on behalf of American clients. I’m pretty good at following US English standards because I’ve been doing it for a long time, but the odd Britishism slips through and Grammarly usually catches it (although a standard spell checker would too, I suppose).

“Think of how poorly the average person writes, and realize half of them write worse than that.”

(George Carlin or something, quote's veracity depends on what you mean by “average.”)

I think everybody could benefit from having something like Grammarly on their computer. None of us writes perfectly, and it's always beneficial to strive for improvement.

People who haven't heard of LLMs