This form of ethics is a useful tool because if we have a business deal in which one person comes out on top at the expense of the other person, trust is destroyed. Continued business will not be guaranteed. I certainly would not engage in business with someone who was trying to gain all the advantages while leaving me in the dust. I may fall for it once, but not twice.
To ensure repeat business, which is what every business wants, everyone must gain from the transaction. No one feels cheated or resentful. All-around good-will prevails and everyone benefits.