I was told once by a physician who was, at the time, looking at my broken collarbone, that the collarbone is in fact designed to break when a certain amount of force is exerted upon it. This "break" sort of short-circuits the force of an impact on the shoulder or arm and keeps the impact from reaching your neck and/or head, causing spinal injuries or head trauma. So the fragile collarbone is actually a design feature of the human body.
Maybe the doc was dumbing it down for me, but it made sense at the time.
There's what people want to hear, there's what people want to believe, there's everything else, then there's the truth!