Base models don't write like that. This appears during RLHF. It's not totally clear why*, but probably a large part of the answer is that this style looks great to human reviewers, and only starts looking terrible once you get to play around with the released model and realise it talks like that all the time.

* The technical term is "mode collapse", see [1][2]

[1] https://en.wikipedia.org/wiki/Mode_collapse

[2] https://gwern.net/doc/reinforcement-learning/preference-lear...