There is an old German fable about porcupines who need to huddle together for warmth, but are in danger of hurting each other with their spines. When they find the optimum distance to share each other's warmth without putting each other's eyes out, their state of contrived cooperation is called good manners. Well, those old German fabulists certainly knew a thing or two. When you acknowledge other people politely, the signal goes out, "I'm here. You're there. I'm staying here. You're staying there. Aren't we both glad we sorted that out?" When people don't acknowledge each other politely, the lesson from the porcupine fable is unmistakeable. "Freeze or get stabbed, mate. It's your choice.
— Lynne Truss
fablegood-mannerspoliteness