You're quite naive. My wife maxes out on prescription pain killers that her (really quite good) pain doc gives her. It means laying in bed doesn't cause constant pain, but everything else (including showering or sitting in a chair) is unbearable after a short time.
We know so much less about the human body than we think we do. When giving birth to our first son, she was given the maximum dose epideral and was told she wouldn't be able to walk for a few days because of intense numbness. Not only did she walk to the bathroom shortly after giving birth, but it didn't even lessen the pain.
Not everybody responds to and gets the benefits of modern medicine as we'd like. I'm grateful that medicine does work on me and my children though.
In the US you only got the problem that the usually subscribed extended-release pain killer only works 2/3 of the period, but everywhere else this is a solved problem with its 4-6 hours cycle.