The Biopsychosocial Model is the best model that we have for addictions and compulsions today. It tells us that this is not a brain chemistry problem alone, it's not a psychological problem alone and it's not a sociological problem alone. Each of these are contributing factors.
Let's look at the societal components. Now I'm going to be talking about alcoholism, but you can extrapolate this into pornography addiction or any compulsive activity.