It's about caffeine and carbonation as much as sugar. Caffeine and sugar are highly addictive substances, with obvious habit-forming potential. Carbonation is a

It's about caffeine and carbonation as much as sugar. Caffeine and sugar are highly addictive substances, with obvious habit-forming potential. Carbonation is a unique effect that stimulates and satisfies people, and probably provides a physical "hook" for addiction, like how many heroin addicts crave the feeling of the needle.