Why do business ethics matter?
Without trust between buyers and sellers, it becomes exceedingly difficult to sustain any sort of business relationship in the short or long term. The reality is that business scenarios come with a variety of temptations that undermine trust: preferring certain customers over others, withholding critical information from a counterparty, or purposely omitting information when acting on either side of a transaction.
Most companies will have a written policies and procedures manual that outlines specifically how an employee is required to behave within the corporate structure, but much of what makes business ethics lies in the unsaid, everyday behavior that signifies trust between clients and colleagues. Really, what this boils down to is maintaining a standard of mutual respect in interpersonal interactions and committing to doing business above board.