Both my father and uncle made it through college and medical school without loans, but with scholarships, savings and working, and yet both found ways to fulfill their military obligations to this country without adversely affecting their careers. Hell, my uncle was drafted and spent the better part of 2 years half a world away from his medical training in the early 1970s. Yet he still managed to keep his career going once he was done. Was it something he wanted to do? No, but he did it with pride and honor. And he was never an "unmotivated soldier," as you threaten to be.
You're a metrosexual, aren't you?
No, I would say that YOU don't get it. Involuntary servitude is not cheap, either for the government or the individuals involved. It is a profoundly stupid idea and accentuate many of the things that are currently wrong with the government. One of the things that makes the US military great is that it is semi-privatized in the sense that it isn't a mandatory social program. And we really don't have a need for this kind of program anyway; it reeks of another socialist boondoggle that will suck money and deliver few results.
Will it stop a young persons career ambitions? No, it will not "stop" them in the average case, but it will impact them economically over the long run any way you slice it. It is, in effect, another kind of tax. I've seen the effectiveness of such programs in countries that actually do this, and the effect it has on the young adults that go through it; we don't want to be inflicting the same mess on our own young adults. Involuntary servitude is bullshit; it is the same reason conservatives nominally abhor taxes.
And before you get all self-righteous about your uncle being in the military or some such nonsense, I am a former combat soldier in Uncle Sam's Army who understands precisely how these things work. I was motivated because I chose to do it, and the military actively states that they do not want anybody in it that doesn't want to be there. It is why they will terminate service contracts of people who want out even though their contract isn't up. A soldier that doesn't want to be their is worse than a soldier who isn't there at all.
Unlike many armchair warriors, I recognize that military service has a real cost associated with it that is detrimental to the individual in many cases. Many people have no business being in the military and the US would not be served well by forcing them to be there. That aside, it is horribly inefficient economically and the US does not need yet another drag on its economy.