Why isn't the upperclass serving in the military?

There is no shortage of people pointing out that today's upperclass are not serving in the military. Ben Stein just ran another piece about this in Sunday's NYT. And you consistently hear about how only a couple members of congress have children in the military. Why is this? There is a tendency to answer by pointing to a sense of declining national responsibility that hasn't been strong since Brokaw's "greatest generation". But this answer really doesn't hold up to scrutiny and we are past a period where national responsibility was defined by serving in the military.

So what are the structural reasons for declining upperclass representation in the military? The all encompassing, obvious answer is that the military isn't attractive to many upperclass youth when stacked up against other options. Although the leadership, management and crisis response lessons learned as a Junior Officer are second to none, the military often doesn't give people that same amount of entrepreneurial freedom found in the civilian world.

Should the nation be concerned? No. The military is going to function well no matter its makeup; it doesn't need upperclass representation to work better, an argument that in fact smacks of elitism. The one argument often used is the "I care about my own" argument which states that if more members of Congress had children serving, the debate around going to war would be more considered. However, war's cost and its impact on the balance of power are probably already enough to hold Congressional attention.