From the linked NEC page...

NEC has put these policies in place to protect you, the consumer, from dealers who have no knowledge of the products, provide no support and in some cases misrepresent the product availability and history.

This is such a farce. MAP policies don't exist to protect the consumer, they exist to support quasi-legal price fixing. The record companies were a little too heavy-handed with their MAP policies which lead to that oh-so-publicized lawsuit where we all signed up to receive our cut of the actual and punitive damages (which I am quite sure I'll never see anyway.) MAP in most cases is blatantly anticompetitive and if we had an FTC with some balls, the whole practce would be illegal.