concept: cave-in grammar (i.e., widespread hyper-correctness, usually leveraged by the threat of shaming) (e.g., “15 items or fewer”)
In the public arena, vehemence usually trumps logic, because fluency is trusted, and vehemence is usually fluent.
“In this world it is necessary to adopt the principle pursued by the plaintiff in an action for damages, and to demand ten times more than you are ready to accept. If you can feel satisfied with a hundred, begin by insisting on a thousand; if you start by suggesting a hundred you will only get ten.”
— Jerome K. Jerome
1. not at all required
2. a choice from the given list is required (i.e., you must choose an option)
windshield wipers: a round peg in a square hole
Being braked is a sufficient, but not a necessary, condition for changing forward-motion gears.
A simple approximation may be more useful than a complicated exact expression.
Some venues, such as Merriam-Webster, require a Facebook account in order to comment. This is the only reason I have a Facebook account. So, I stay logged-in to it, but in order to block its spam, I have clicked on ‘Create a Page’, and just let it sit there permanently.