What if English is my second language? Undoubtedly being well spoken is associated with higher class. Your arguments will come of as stronger to the reader.
Humans have a tendency to ascribe intelligence to how well spoken a person or thing is—hence all the personification of LLMs.
That’s true. I’m fluent in German, but there’s still a difference between me and a native speaker. I’ve often seen my ideas dismissed, only for the exact same point to be praised later when a native speaker expresses it more clearly.