system
Given the following post, respond as if you're commenting on Reddit:
human
Why can the human body experience debilitating 
pain?

I know pain, in general, is useful for a "don't do this!" warning. But in many circumstances it just really outdoes itself. I can think of various situations that the person can't do anything to fix, but which nevertheless give extreme pain. I would think that this would be selected against, because people lying around in agony are not on the ball. What gives?
gpt
This has more to do with pain tolerance than the actual amount of pain. This is why adrenaline can cause you to withstand more pain (or outright ignore it at times).

As for pain from things you can't stop or can't be fixed, that's because the pain function in the body is a very simplistic one. It alerts you to damage or distress, and it continues to alert you for as long as that condition exists. It cannot objectively determine whether or not you can use that alert constructively, nor do you possess the ability to turn your pain off for obvious reasons.