Because it is said that humans never satisfy themselves, that they are given one thing and always want something else. And this is said with erroneous contempt, since it is one of the greatest virtues that the species has and that makes it superior to the animals that are satisfied with what they have.
The quote reflects on the nature of human desire, suggesting that people are often dissatisfied and continuously seek more than what they currently possess. This perspective is sometimes viewed with disdain, labeling it as a flaw in human character. However, this attitude overlooks a fundamental aspect of humanity: the drive to aspire for greater things.
According to Steinbeck, this insatiability is not a weakness but a significant virtue of the human species. Unlike animals, which are content with their circumstances, humans strive for improvement and growth, which ultimately sets them apart and elevates their existence. This continual quest for something beyond their grasp is essential to advancement and development.