Earlier quoted context omitted.
Because they are a human being.
And every human being is entitled to the same amount of wealth? Good luck with that battle.
Within families we do not keep tallies of who owes what to whom. My parents did not present me on my 18th birthday with an itemized bill of what I had cost them. Nor did I do that to my children. Economics should be a servant of society, not vice versa.
Unfair distributions of dignity, income, wealth, and power seem easier to accomplish within large entities (corporations, governments) compared to families or tribes. Division of labor and specialization make it easier to justify unequal and unfair treatment.
What changes do we make to our values and ways of organizing ourselves, to have more just outcomes?