In our society, the place of the upper class is leadership. They are our parents. They don't have to choose leadership, but they are already leaders. Some, like politicians and some corporate leaders, work hard to be leaders. But others, like entertainment celebrities, inherited wealth, or sports stars are leaders whether they want to be or not.
In our society, the middle class are the masses. They are the peers, the siblings, those who hold the social position of equality, for whom laws and authority work.
In our society, the lower class are the dependents. They are the children, the pitiful ones, those for whom everything must be given. They are mocked for they never "grow up" and become adults.
But the fact is, the lower class must exist, for we must have people to pity, people to mock. We must have the "dysfunctional" member of the family to blame, or else we must blame the leadership for being inadequate for the job. We may talk about "ending homelessness" or a "war on poverty", but the leadership must create homelessness and poverty as quickly as they create "solutions." It is a social mandate.