You could say the same for overeating, or drinking too much. Some people have no issue with overeating, but at least in America most people are too fat. ie, they cannot intake calories responsibly.
When something involves a small percentage of the population, it's typically an individual issue/failure. When it becomes the vast majority of people, like in the case of obesity, you have to seriously consider that the issue is in large part systemic. I seriously doubt, for instance, that in the last 20-30 years, 80% of the American population suddenly woke up and lost all willpower when it comes to food, especially now that the obesity problem appears to be spreading to other countries.