The incentive to come together as a group is not about how much an individual is paid, but to come together over a common ground and influence change that benefits the many over the few. Income is one of the most common things to throw out there because it encompasses pretty much everyone's life.
An individual can be paid handsomely, even if the group average is a fraction of the individual's number. Though you believe you are paid well, and you may very well be, it does not mean actions do not happen to suppress the momentum of someone sitting a desk or two away working toward the same goal as you.