Middle Class

The presence of a middle class perpetuates the idea that the poor are to be blamed for their poverty. For the wealthy to decry that the avg  poor person  should pull themselves up by their bootstraps to a place of wealth and  prestige is far-fetched, if not outright  ridiculous notion and neither the wealthy or the poor really believe such is possible on a mass scale. Therefore the Middle class services an important social  cohesive function. The wealthy need the presence of a comfortable "middle class" as as a realistic outcome to justify their ethics to the poor.  

However the poor probably don't need the middle class. The middle class serves a  as buffer between the wealthy and poor. If not for the middle class the poor would have more more  power to wield in labor and distribution. If the poor could boot strap a business to market directly to the rich, then the redistribution of wealth would be more direct, rich to poor and you would have more upward and downward mobility leading to less social stability.  Both the rich and the poor have essentially little to lose  in taking risk in our modern economy because of it's social class stability. No matter what you do today, you will probably  be as rich or poor tomorrow as you are today. In a sense recklessness is encouraged on both ends because there is little to lose. 

In contrast  the middle class are then required  to be the responsible and fiscally conservative ones that maintain the social stability. They are the ones that are expected to plan and save in times of plenty and then spend that saving to maintain economic continuity through times of  recession.