The truth is indeed that legal tender is simply a legal device to force people to accept in fulfilment of a contract something they never intended when they made the contract. It becomes thus, in certain circumstances, a factor that intensifies the uncertainty of dealings and consists, as Lord Farrer also remarked in the same context, ‘in substituting for the free operation of voluntary contract, and a law which simply enforces the performance of such contracts, an artificial construction of contracts such as would never occur to the parties unless forced upon them by an arbitrary law.from this source

Why is the draft for Jury Duty okay, but not for Military Duty? The following from Dr. Henderson is the succinct and often repeated explanation from the Econo-tarian vantage point.

In his testimony before the commission, Mr. Westmoreland said he did not want to command an army of mercenaries. Mr. Friedman interrupted, “General, would you rather command an army of slaves?” Mr. Westmoreland replied, “I don’t like to hear our patriotic draftees referred to as slaves.” Mr. Friedman then retorted, “I don’t like to hear our patriotic volunteers referred to as mercenaries. If they are mercenaries, then I, sir, am a mercenary professor, and you, sir, are a mercenary general; we are served by mercenary physicians, we use a mercenary lawyer, and we get our meat from a mercenary butcher.” from this

It of course answers only the glory of volunteers to the military.