Most people write badly. Much of the text on the public Internet is written by professional writers, who tend to write less badly.

When people use LLMs to generate text, they often ask it to write like a professional. (I haven't tried, but I assume that if you ask an LLM to write like a Reddit troll it will use a different set of forms.)

When you ask an LLM to write like a professional writer, it will aim to sound like a professional writer. They do in fact, and in speech, use words like "delve" and "robust" because they spend years cultivating their vocabularies.

Professional writers are comfortable with punctuation marks and know the difference between the em dash and the en dash, and when to use each versus other marks. (The typical non-professional cannot manage to use the apostrophe, much less the marks that require judgement.)

And a lot of them end up writing business content at some point in their careers. Which leads to an interesting mash where you may get "leverage" used as a verb alongside some of the other pattern tropes.

Because business writing is its own universe. LinkedIn has been swimming in content that would be flagged as LLM-generated for at least 10 years, long before ChatGPT landed.