New York attorney here. You're kind of getting it, though put in a silly way. It's not that "vague, bad stuff will happen" it's that, in common law jurisdictions at least, precedent controls. So if you use language that has been upheld for decades or even centuries you can be as confident as possible that whatever you're doing will also be upheld. Any novelty or variation introduces greater risk of a ruling against you. This naturally creates inertia and a conservative approach in legal practice.