To kind of piggyback off of kleinbl00's example and some of the ground he's already covered, English has "rules" in the sense of "ideally speaking, this is what you're supposed to do." Unfortunately, the rules are more like guidelines and because we borrow elements from Latin and Germanic languages, culturally entrenched coloquialisms, and academic fads and trends, the rules are all muddled up. Combined that with the fact that it's very easy to be ambiguous in English, both intentionally and unintentionally, for some degrees and studies, a heavy focus on grammar is necessary.
Edit: Personal anecdote, I collect antique books. There's a noticeable difference in editing styles starting in books from the '50s. The further back you go, the more noticeable the differences become. Punctuation becomes weird. Syntax gets weird. Shit, even something that you take for granted like indentation and spacing gets weird.