Theoretical contribution
They argue that writers traditionally identify addiction with problematic patterns of consumption related to "harmful" goods like "tobacco, drugs and alcohol."
By applying the same concept to the consumption of supposedly "beneficial" goods like theater, Castiglione and Infante attempt to expand the horizon of behaviors to which the concept might apply.
Simultaneously, the authors extend the appeal of their study beyond those few scholars interested strictly in theater attendance and even those many more interested in the consumption of cultural goods.
If Castiglione and Infante successfully apply Becker and Murphy's model, then their work may invite the attention of addiction scholars, public policy scholars, more general microeconomists, anthropologists, sociologists, and others.
To oversimplify, if their empirical contribution addresses the question, "so what?," then their theoretical contribution addresses the question, "who cares?"