What twaddle!
He was supposedly an intelligent human being, and yet apparently fails to realise that despite the illegality of what he was doing, the only realistic prospect from it was the one he got. I care not a jot that the guy was on prescription painkillers, and the drug companies hardly forced proressively stronger painkillers on the guy! He was a rich and privilidged fool and as with many similar peoe in his position, he managed to find yet another way to spend his obscene wealth-drugs. Because thats what you do when you are loaded and famous. Hence Whitney, Jackson, Heath Ledger, Marilyn Monroe, the list is endless. I am in pain most days. Sometimes the prescription drugs I have don't touch it. I have yet to pump mysekf full off illegal crap as a result. Utter tosh 
We, for all intents and purposes, are just a function of our brain health. Like I said in my earlier post, there are multiple reward pathways in the brain. There are also variations on these pathways, some of which are convoluted. Have you ever found it enjoyable to read and learn something? If so, you have a much shorter reward pathway for cannabinoid receptors than someone who does not enjoy reading and learning. I'm using that example as an analogy as to why some people can take pain pills and not become addicted, while others are totally dependent after a short prescription of them.
It is quite obvious that being rich and famous brings a person in contact (whether they want to be or not) with drugs. About the only safe option is to never try them at all.
Your rationale of "Because thats what you do when you are loaded and famous." is totally off base. As is "I have yet to pump mysekf full of illegal crap as a result". Why would you pump yourself full of illegal opiate based drugs that, by your own admission, don't even take your pain away? The answer in your case is that you wouldn't, because you gain nothing from it.
Here is a good website that covers the physiology of addiction
http://ibgwww.colorado.edu/cadd/a_drug/essays/essay4.htm