I imagine that, corpus aside, it uses personal pronouns for much the same reason that humans do. It's useful for it to have a self-referential vector embedding, and this lets it solve problems faster and more efficiently.
Impersonating a human does nothing to help it solve problems faster, quite the contrary in fact, it has to waste even more time coming up with human-like speech patterns to present the work done.
It shouldn’t assume any personality unless I explicitly tell it to. It is a tool until I tell it otherwise.
Might want to rethink your statement after going again through what it does exactly. No need to sound more human. but it gives more tokens to "think" like a human committing brain-time to a problem would