What upside is there to labeling your content as AI generated (except when you are showing some novel way to use AI)?
It’s the same reason recipe websites don’t honestly label that they ripped off other recipe websites: it would train users to go to the source.
For example, consider this project where I also complained about atrocious writing: https://news.ycombinator.com/item?id=48876506. I think this is really just someone who wanted to "create" something, I don't think this is in the same category as recipe/blog spam. I don't think the person who put this online thinks that this landing page is worse than any other programming language website.