system
Given the following post, respond as if you're commenting on Reddit:
human
Why are humans able to feel excruciating pain?

I understand that human need to feel pain in order to signal our body that we are doing something hurtful to it. But we the need to have different levels of pain? Would it not be more convenient if a horrible leg break hurt like being pricked by a needle? I would still realize that something is wrong with my leg and try to fix it.
gpt
There isn't a reason, or "why", for evolution. It merely happens by chance and whatever seems to be able to last long enough to be passed on to the next generation, does. To answer your question, though, it may have something to do with nerve endings and cell damage. The more nerve endings and cells that are damaged in a harmful incident, the more signals are sent to the brain to say that something's wrong. 

Some injuries have more of an effect on the abilities of an animal than others. If you treated a serious injury, such as breaking a leg, just the same as if you received some small scratch, it wouldn't be as important as if you felt it in a higher magnitude than that small scratch. Therefore, you would perhaps do less to treat it, and you may do less to prevent future occurrences if you do survive the aftermath. Evolution isn't about being convenient and in the better interest of the organism. It may be in some cases, but for the most part only those who responded the most severely to the break, or did the most to avoid that situation, are the ones that survive the most frequently to continue on with the next generation.