Typically draft and volunteer armies are culled from the poor. For example, in the old days you could avoid the draft by paying a fee; so only poor people had to go to war. I prefer the Roman model: all landowners (rich people) have to serve in the army at some point or another. Of course that evolved into feudalism which wasn't so great.
Take the Swiss style. Their citizens are forced to enter military training for two years, mandatory. It's a condition of citizenship. Incidentally, Switzerland has never been invaded. The founding fathers proposed a similar system, believing standing armies to be too corruptible. Cue Eisenhower "Military-industrial complex" speech.
Anyway, if our country were under attack, they wouldn't have to draft me, I'd sign up. As it is right now though, our army is just a corrupt, bloated, waste of resources.