In a business setting, managers sometimes do not realize they are behaving unethically, primarily because they

This was explained on Essentials of Strategic Management written b y Charles W. L. Hill, and Gareth R. Jones p. 46.

The authors explained this on The Roots of Unethical Behavior that managers are still individuals, it means that a person's behavior still relies on personal ethics.

Another reason is that managers at times might not see the relationship between a business approach and the ethical space. They might believe that it is merely a business decision and they go beyond entering the ethical dimension.

And last is the organizational economic approach to have a goal which can push them to disregard their behavior.