In part, you've answered your own question. People have had their lives ruined by substance abuse, whether painkillers, alcohol, tobacco, or prescription or street drugs. The operative word is abuse.

Unfortunately, what should be a medical issue has become a political one.
Google: politics of pain

The risk of addiction is actually very small among chronic pain patients without a previous history or propensity for abuse, or psychological problem (which is what addiction is).
http://www.health.com/health/conditi...9482_1,00.html
http://www.chronicpainrevolutions.co...ic-pain/75.htm

This is not to say that prescription painkillers are without inherent risks.
http://www.stoppain.org/pcd/content/...tablishing.asp

I can commiserate with the weight gain. I found some help with the diet in the back of this free book/download:
http://intractablepaindisease.com/
I'm also getting some good results with pain levels from the hormone replacement (depleted by chronic pain) mentioned in the same book.
http://neurotalk.psychcentral.com/thread156416.html

Doc