In 1991, Cato Institute's Doug Bandow made an argument about America not needing conscription. In it, he asserts:

Although public dissatisfaction eventually ended American involvement in Vietnam, it took years for political opposition to build, a period during which tens of thousands of Americans died needlessly. An AVF might have ended the war far sooner, since young people would simply have stopped volunteering.
I wonder how the numbers bear out in recruitment/retention figures compared to the popular opinion of the conduct of the Iraq War II. But then again, is there really any direct correlation between recruitment/retention and public opinion? After all, the military burden of the last 10 years has been carried heavily by one demographic and is not necessarily reflective of national opinions. And low retention levels ended up only affecting recruitment standards and enlistment bonuses.

Of course, for Bandow's argument to be valid on this point, he must assume that ending the conflict on unfavorable terms is preferable to having a draft system in place (which says alot about his view on national interests).

Bandow eventually concludes:

Our prob- lem today is not a military filled with those who want to be there but a political leadership willing to risk war for peripheral interests. A draft cannot change that. If it could, we would not have had to construct a memorial to 58,000 people who died in a purposeless war two decades ago.
I don't think Ricks (or myself) would argue that an all-volunteer military is inherently problematic, but instead that it carries risks of it own, some of which are very costly and questionable and could be addressed by an alternative system.