Some people do not just do something wrong in a weak moment though they say that they did because of this limitation or because they are not sure about what is the right thing to do. I guess most of the time some people know exactly what they are doing and why. Self-interest, personal gain, ambition, and downright greed are at the bottom of a lot of unethical activity.
As I have observed pressure can drive people to do things they wouldn’t normally do and they also try to justify with this term..PRESSURE. Pressure to succeed, pressure to get ahead, pressure to meet deadlines and expectations, pressure from co-workers, bosses, customers, or vendors to engage in unethical activities or at least look the other way.
There are those who simply never learned or do not care about ethical values and they justify themselves with simple ignorance. Since they have no personal ethical values, they do not have any basis for understanding or applying ethical standards. These people do not think about right and wrong. They only think, "What’s in it for me?" and "Can I get away with it?