There are many reasons why someone might choose to do drugs, drink alcohol, have reckless sex, drive too fast, or otherwise make unhealthy and unwise decisions. Anyone can overcome addiction, but when the alternative to using includes depression, suicidal ideation (what kind of life do you have left if you're no longer high, just in withdrawal?) debt, isolation and the complete lack of a support system (similar to attitudes you demonstrated in your post), then it does not surprise me in the slightest that people relapse when they think they have no positive life options.

He was clean for 23 years, but maybe that was 23 years of excruciating effort and dealing with media pressure that he could no longer cope with, who knows? People relapse for all kinds of reasons, from thinking they can "handle it now", to being triggered by some sort of change or life event. Recovery seems to be a constant thing one has to be mindful of, sure - but if you're saying that the government has no responsibility to even try to decrease the unnecessary deaths associated with laced drugs, then that's really disappointing given that a lot of addicts have had the sorts of experiences you don't seem to be able to understand or identify with.