Why is it that people with alcoholism often not realize they are alcoholics?

Old saying-Denial: Is not just a river in egypt. All of us can develop denial about many important things - why we overeat, that we are overweight or obese, why we don't exercise, and make a variety of excuses to ourselves that either deny the problem, or minimize it, or project it on someone else. Same with alcohol and drug abuse, particularly because they carry more social stigma in our society.