His focus no longer is on life and family but rather on his chemical of choice. This preoccupation sets aside family and job responsibilities and lets the alcoholic focus on his chemical. There are certainly genetic factors which play a part in addiction. We'll see families where everyone, father, mother, sons and daughters are addicted. We also see people who use in an abusive manner over a long time who cross the line into addiction.
Environment can play a function as well.
If you grow up in Hells Angels as a child, you'll naturally be exposed to drug use, or alcohol use as a part of your life. Mental health issues can also play a factor. People who are sociopathic or borderline are more likely to be addicted. People with anxiety disorders, or depression, may try to treat their disorders by themselves with alcohol. Therefore, there's no real separation between the alcoholic or addict.