There is one different aspect to this issue....it’s a legal drug (unlike Meth, crack, cocaine, etc). So all of these folks with long-term back-pain found their wonder drug....all legal in nature.
As you look at the usage issue....even the people with pain came to discover that as they used for long-term, it became less effective, and they had to double-up on the wonder drug. This is how the pain-clinics in Florida popped up and helped to hand out additional prescriptions and gave people as much as they wanted.
Methamphetamine and cocaine are both legal Schedule II drugs.
I think people have simply forgotten how to cope with pain, our great, great grandparents certainly had more pain to cope with than we do now simply due to a much more physically demanding lifestyle but most of them did not depend on painkilling medicines. I myself have spent years in constant pain and took no painkillers at all, not even aspirin. Some may think this crazy but what seems to relieve my aches and pains better than medicine now is simply to take a very hot shower and then turn the water from hot to pure cold and stand there under the shower for another ten minutes. I am 73 and have only minor aches now, I can walk faster than almost anyone I know and can still run for short distances.
One thing I am fairly sure of is that if you take strong pain medications for an extended period you will have worse pain than ever if you stop and that results in not being able to get along without them. The brain has amazing power to turn off pain if people could learn to use that power.