English, like every language, has fundamental rules governing grammar, punctuation, and other aspects. However, it also has many other rules that are stylistic, such as not starting a sentence with a digit. Stylistic rules can serve a useful purpose, but they can also be quite arbitrary. They can even differ between different kinds of text; for example, we usually do not use contracted negative forms (e.g., "didn't") in academic writing, but they are perfectly acceptable to use in other forms of writing.