First, let me start by prefacing my statements by making it clear that I am not an expert in the area of alcoholism or any type of addiction. I have spent a significant amount of time in self-learning relating to the subject at hand and do have a medical background, but have in no way obtained the credentials to be considered an expert.
Doing a meta-analysis of studies relating to the topic, the best answer science can give us at this point concerning the causes behind addiction is "we don't know". Anybody who claims otherwise is cherry-picking studies that fit their bias. It wouldn't take longer than about 5-10 minutes on PubMed or any university library search engine to present them with well done studies concluding the exact opposite. And, in the end, science is always just a series of better wrong answers. Our understanding is always limited, and thus, our conclusions are always proven false in time.
One intriguing aspect of addiction, that is rarely talked about, is what interests me most. Specifically, that is whether or not addicts have any obligation, moral or otherwise, to actively avoid their addiction. It seems to me that most people consider "recovery" to be universally positive and something to be desired. In reality, "recovery" is usually a daily battle for the addict and the avoidance of their substance of choice can be downright miserable on a daily basis. I think there is a real question as to whether being miserable and living an extra 10-20 years in that miserable state is a desirable goal. Most addicts are perfectly content when using, and there is a legitimate argument to made that a shorter life lived in a more content state is better than a longer life lived in a miserable state. Of course, exactly how large a difference in lifespan we are talking about certainly plays a role in that debate.
Many people would argue that regardless of the above issue, the addict has an obligation to "recover" because the addict has a tendency to cause emotional (and sometimes physical) torment to those close to them. However, that argument, at its core, is one that implicitly implies that the emotional well-being of the addict's loved ones are inherantly more important than the emotional well-being of the addict themselves. I'm not sure that should be a generally accepted premise.
Anyways, sorry for the long diatribe on a subject that probably doesn't need any more fuel on the fire. This thread probably doesn't even belong in a sports forum, but I just though I would add some thoughts to consider. What's clear to me is that addiction is not black and white and that while most arguments have some partial validity to them, they do not paint the entire picture.