John Rawls famously argued for his maximin principle of distributive justice in A Theory of Justice. Essentially, the principle states that we ought only to allow unequal distribution of resources insofar as it increases the welfare of the most disadvantaged members of society. Rawls basically accepts an egalitarian principle, that everyone deserves a (roughly) equal distribution of society's good. But, because of the realities of human life, we recognize that giving some people a larger share of the resources may result in raising the living standards of everyone, including the worst off. The worst-off could thus not rationally object to the inequality, because they would personally be even worse-off if such inequality were eradicated.
There's been much debate about this principle and the arguments surrounding it. For me, one of the most interesting critiques comes from G. A. Cohen. He argues that if we expect our society to be just, we would imagine that the citizens in the society endorse the principles of a just society. The problem this raises for the maximin principle is that if everyone endorses the fundamental egalitarian premise, then there could be no justification for inequality. Everyone would fulfill the duties of their position in society to the best of their abilities, without anyone thinking they deserved a larger share of the resources for doing so.
In this way, the maximin principle wouldn't necessarily be wrong, just irrelevant. There would be no need for inequality because everyone would do what would contribute most to the general welfare. No one would argue that doing their part meant they deserve more, because by hypothesis, they're egalitarians.
Now there's much more to be said about this argument, obviously, and some people disagree with Cohen (others think that the difference between the two views is rather trivial.) And you might say that even if Cohen is right in terms of moral theory, Rawls' principle is the best we could ever hope to achieve in reality. Perhaps that's true, though I think it's best to remain optimistic about human potential. Regardless, Cohen's point is still extremely important either way.
I first came across Cohen's argument in If You're an Egalitarian, How Come You're So Right?. There's a lot to say about this book, but what's relevant to this post is the way the titular question is addressed. It's a question asked of an individual. This is important because even if you could justify the maximin as a pragmatic reaction to the world world, that still doesn't justify any individual demanding more of society's goods in order to perform their valuable services.
If you study economics, you might try to think of ways to construct policies that incentivize people to do what's best for society. And it's probably great that people do that. But just because we realize that on a large scale, we need to implement such incentives to produce good results, it does not mean that any one is justified in failing to do what's right in a society without those incentives.
I fear that, in a world that seems to value studying economics over ethics, many people confuse what is necessary for what is just. If you discover that modeling human behavior is best done by assuming everyone is a self-interested value-maximizer, you might think that it's perfectly fine for you to act that way in your life. But in truth, that is a complete non-sequitur. What people in fact do has no logical connection to what people should do. Thinking too much about the former might cause you to neglect thinking about the latter, and that can easily make you a worse person.