Scamming exploits the benevolent optimistic attitude of trade. It uses the expectation and planning of the victim, that some compensation will come their way and "pockets" the benefit without planning to return something of equal value.
More elaborate scams will try to evoke other benevolent ideas and e.g. appeal to empathy or "luck" of encountering a really good business opportunit. They will actively encourage the victim to believe that it is a fair exchange, when it is already planned to not be one.