I have chronic pain, and I could tell you what's bad about that, which I think might be applicable to pain more broadly.

Pain doesn't always serve its purpose of keeping one out of trouble, and when it doesn't, it's distracting. It sometimes makes it difficult to get up and go, much less do anything great. It can be a spirit breaker when it goes on too long, affecting mental stamina and usefulness as well as physical.

Depending on where the pain is, it can make it difficult to complete tasks in a much more specific way too, by making it difficult to walk or use ones hands. I don't have kids but I imagine it would put a big ole damper on raising them.