Sometimes the "what's in it for me" argument is the only way to reach certain types of people. As materialistic and selfish much of American society has become, it's the argument that reaches a large portion of the people.

Slightly back on topic, does the axiom "don't buy anything American-made that was made on Monday or Friday" still hold true? :D.

also, rationality and reason does not unequivocally lead to egoism. take habermas' "theory of communicative action," which states that the most developed and complex form of rationality is that which is fundamental to when we try to understand each other. a different kind of objectivism, if you will.