I don't know where you got from that anyone deserves pain. All I said is that if you experience pain, you should try to remedy the cause instead of just using generic painkillers. I too had back pain because of my desk job; I acted accordingly.

There's nothing shameful about having pain or treating it with painkillers, but I think there's something wrong with the sentiment that's also often found on Reddit that knees and back just hurt when you're over 35.

While the issue is often rooted in society (through labor or other lifestyle details that are pushed on the individual), it's you who has to live with that body until the end. Rightfully blaming society won't help.

For causes outside of your control, there's nothing to do.

Anyhow, for issues like rheumatic arthritis, there are more targeted drugs than genetic painkillers AFAIK that are taken on a schedule. I have both friends and family who are affected; osteoarthritis is indeed treated with e.g. paracetamol, but is usually accompanied by some sort of therapy.