Suppose a society with three classes of people. A are the very well-off, B are well-off, C are worst-off. The distribution of this classes is shown in the following triangle.
As you see, there is no enough space in B for the people in C, most of the people is condemned to be worst-off.
No matter how effort is spend in C, there is no room in B. The same for B, there is not enough room to be in A.
Going from an upper level to a lower level is very rare, almost impossible.
So, no matter how hard people in C work, there is no room in B for them.
How this can be just? In essence, the well being of a few depends on the ill-being of the majority. This is the kind of society we live.
Now, to consider a society like this:
There is plenty of room in B for people in C if they work hard. The same for B going to A. This society should be more just since if C people make the effort the would go to B, eventually, if all work hard there would be no inequality, all will go to A, but societies are not like this.
Do you know philosophers who explore this line of reasoning?