You seem to think that the "economy" in its (mostly or completely) unregulated form is some kind of ideal. Why? Such an economy is dependent on rational actors and perfect information, neither of which are present in human society.
It seems more reasonable that each human in a group will try to maximize their own economic outcomes as well as to assist the other humans that they personally care about in maximizing their economic outcomes. In the modern world, it's often expected that humans are able to extrapolate that the people that they don't know are similarly worthwhile human beings. So while it's generally considered acceptable to try to maximize things for themselves, doing so while knowingly making other humans worse off is seen as morally detestable.
It's important to remember that humans generally care much less about abstract ideals than they do about themselves, the people they care about, and their social standing. The "economy" as it exists in reality does in fact exist for the benefit of one class of persons: those persons who are willing to tolerate it and have the power to change it. When this real-life economy is no longer tolerated, it is changed, in ways like antitrust legislation, class action lawsuits against companies that participate in wage collusion schemes, and the French Revolution.
It seems more reasonable that each human in a group will try to maximize their own economic outcomes as well as to assist the other humans that they personally care about in maximizing their economic outcomes. In the modern world, it's often expected that humans are able to extrapolate that the people that they don't know are similarly worthwhile human beings. So while it's generally considered acceptable to try to maximize things for themselves, doing so while knowingly making other humans worse off is seen as morally detestable.
It's important to remember that humans generally care much less about abstract ideals than they do about themselves, the people they care about, and their social standing. The "economy" as it exists in reality does in fact exist for the benefit of one class of persons: those persons who are willing to tolerate it and have the power to change it. When this real-life economy is no longer tolerated, it is changed, in ways like antitrust legislation, class action lawsuits against companies that participate in wage collusion schemes, and the French Revolution.