There are certainly many people who are heavy drinkers who do not have a drinking problem. For instance, in college, a lot of young people binge drink and would be classified as 'alcoholic', however, as they progress in life most have no problem.
Also, for those who subscribe to the idea that alcoholism is a symptom of a disease, and not the disease itself, might believe that they can manage their alcohol intake during less stressful times.
I think it is important that we do not paint everyone with the same brush-stroke. As with most things in life, there are many shades of gray. I do not believe alcoholism is black or white, all or nothing... though it's easier to think that.
JMO