Except that by definition, addiction means that we have lost the power of choice. I know this is impossible for people who have not experienced addiction to understand, but being addicted means being unable to stop, even when you want to.
Also, it's important to understand that one of the most imposing characteristics of an addiction is a blind obsession with the substance we're addicted to. Alcoholics, for example, simply cannot comprehend alcohol or it's effects, reasonably. So that their "choices" become the choices of a person who is not capable of thinking reasonably about their own behavior.
Of course. YOU can see that, and so can everyone around the alcoholic who is not also alcoholic, but the alcoholic himself will either simply not see them, or they will not register in his mind as a real consequence. Believe me, I have been there many, many times. And it's inexplicable how the mind simply erases all cognizance of reason and proportion when it comes to the consequences of getting drunk, when you're alcoholic. To an alcoholic, getting drunk is far more than a desire that he can reasonably turn down. It's a blinding obsession that owns him, and will destroy him and everything he loves. It's like living in a nightmare where some evil force inside you just takes over.
Alcoholism is not an "excuse", it's an illness. I know it's much more fun and much easier to just blame the addict and then wash your hands of him/her in the resulting righteous indignation that you feel, but the sad truth is that addictions are a form of mental and physical illness that we still have not found a cure for. And it's terminal. It kills millions and millions of human beings every year, while it does untold harm to their families and to those who love them.
It's a very difficult affliction to understand, and even more frustrating to have to deal with, which often causes a lot of anger and resentment. But it is what it is, and blaming and washing our hands isn't going to help anyone. We need to face it for what it is and try and understand how it works, before we can ever hope to find a way through it, to healing.