That's really what I was referring to. Everyone gets in for different reasons, but once you're in, the motivation is always the same - to get high.
You don't get high on pain killers if you take enough to get rid of the pain. Rush did not show the signs that he was regularly getting high. I doubt that he intentially got high, though he may have occasionally taken too many pills out of frustration when his pain was severe.
Oh, I don't know. There's certainly a "high" to many painkillers, making it more than just withdrawal pain-avoidance, IMO - I had surgery some years ago, and Demerol was part of the post-op pain treatment. And I assure you, that stuff will
definitely get you off if you're so inclined - yes, the pain goes away, but you also feel nice and dreamy and shiny and happy and floaty. It's good stuff - not that I'm interested, now or then, in taking up a recreational Demerol habit, you understand ;)
At some point in the painkiller-addition track, one of two things happens - either the dosage begins to exceed the amount necessary to for the amount of pain, or the pain goes away but the drugs don't. And it's at that point that you're not taking it for pain, but for other reasons, the avoidance of withdrawal being only one.