First of all, weight-and-size-accurate dummies (whatever they're actually called in English) have legitimate uses.

Second, being honest about commiting fraud is counter-productive. Comercial fraud, even though illegal, is still a commercial enterprise at its core and its goal is the same as of any other comercial enterprise: to bring in profit, the more the better. Fraud is not about sending a message on ethics, or showing off someone's character, or helping the marks to keep their money, it's about getting as much money as possible at little cost as possible (with the costs of dealing with legal persecution accounted).