"Since it is inherent for humans to crave variety, the concept of faithfulness is in actuality going against human nature."

Imagine a world without social constraints, where there is no moral obligations to remain faithful to one and monogamy is abolished. Does that mean that humans would not keep to one perpetual partner for life? It is absolute individualism where everyone is selfish to satisfy one's needs first without giving due considerations or having no obligations to another. Would love exist in the form we have perceived it today then? How many people actually stay together or remain so-called "faithful" due to moral obligations or social constraints?

The point is probably moot since no world or culture as we know it can fully exist without some sort of social constraints upon the individual exercised by a larger collective.