Makes sense. Only 18-25 year old, healthy men should be able to vote. Totally makes sense.
And the idea that only those subject to the draft should be voting is absurd as it neglects the rest of the current military.
Along with neglecting every issue that's effected by voting (well, by our representatives) that aren't military/war. Everyone in this country is a stakeholder in these elections.
True all people in the country are stakeholders but not all are similarly exposed to the risks of war (the military is primarily poor and filled with minorities--but that's a separate issue).
Fortunately women will soon be required to register with the selective service so this critique will be outdated.
I haven't found the numbers for economic background prior to joining, but with respect to minorities. The US military is around 75% white. They are underrepresented versus the population as a whole, but still make up a significant chunk of the military.
https://mic.com/articles/59699/one-stat-about-the-u-s-milita...
At least circa 2008, people from lower class (financial) backgrounds were underrepresented versus their middle class and upper class peers in the US military.
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This doesn't mean that minorities and the poor aren't targeted for enlistment. They almost certainly are, but by the raw numbers, they aren't filling the military.