The frequency of a behavior is not what makes that behavior an addiction.
For example, take walking. Most people take hundreds, if not thousands of steps each day. Nevertheless walking is not considered an addiction in most cases. Why? It is not something that the organism must do to survive, it is a voluntary behavior, yet no-one would think you addicted to walking because you did not take the elevator or did not drive the 400 yards to the supermarket. On the contrary, it is generally recommended to walk whenever you can, for reasons of health.
The urge for a behavior does not make that behavior an addiction, either.
For example, most people feel a strong urge to eat, drink, sleep, defecate, and none of these behaviors are considered an addiction. Maybe sexuality is a physical need, and in the absence of a partner masturbation is better than "going hungry"?
The problem with masturbation is that even scientists find it difficult to look at it neutrally, because it is hard not to see it through the filter of our cultural norms on sexuality. Walking is not a taboo, it can be done in public and with anyone you want. Eating and sleeping can be done in public, although to a lesser degree, and even defecating is not suppressed with the same vehemence as sexuality: a man urinating against a tree in a park is not something you find overly idyllic, but most people would not call the police, because they know how it hurts to hold in, while a man masturbating in the same spot will find himself arrested rather quickly. Masturbation has been forbidden by religious rules, thought to cause illnesses, and today has the stigma of presumably signifying an inability to find a partner.
Once you strip away the morals and prejudices and look at masturbation with a cold eye, you will realize that many children indulge in it and only take a break while they are dressed. Children stop masturbating (in the presence of witnesses) only if they experience negative reactions to their behavior, i.e. only once they learn the norm that masturbation is something to be ashamed of.
It is this normative view from which a masturbating teenager might appear addicted. For the scientist, masturbation is a normal and healthy behavior, especially in a 13 year old teenager, who has gained a new function and a new level of sensory pleasure. For the scientist, it appears unnatural not to explore this ability.
As for masturbation in adults, as far back as 1948 Kinsey found that masturbation alleviates nervous tension and that men who masturbate lead a more balanced life. Sexuality appears not as voluntary as riding a bike, but rather has strong physiological and psychological effects that make sex appear to be normal and healthy behavior for an adult human being.
And if we have come to consider sleep lengths between four and twelve hours to be perfectly normal for adults of our species, why would we not be equally broadminded regarding sexuality? Maybe because indulging in any kind of pleasure is frowned upon in our performance-oriented society?
- Kinsey, A. C., Pomeroy, W. B., & Martin, C. E. (1948). Sexual Behavior in the Human Male. Philadelphia: W. B. Saunders.