Right, and that doesn't seem good to me, but I don't think the fallout from student loans will be anywhere near the fallout from defaulted mortgages in 2008ish because they just aren't as as levered.
So it's terrible for the people involved, but not directly bad for society as a whole (but probably still bad in its second and third order consequences).
OP didn't say to join the military to get an education he said to do it as an alternative to college. It's a good career path that teaches useful skills. Most people in the military aren't employed in combat roles.
It's a shame you're getting downvoted, since you make good points. For many people the expected value of college is negative. I also think HN is unnecessarily critical of the military. I work with lots of people who served in the military for a few years after high school before eventually going back to college and they seem happy with the decision.
But as far as I know student loans aren't securitized and leveraged in the same way as mortgages were, so I'm not sure that the fall out will be as bad.
The root problem (as others have noted) is too many people are encouraged to go to college and even though most majors don't make economic sense students (rightly) feel that they need a college degree to be a competitive applicant for good jobs. Maybe I'm just in an ideological bubble, but it seems like there's pretty good agreement on this issue, but no real way to do anything about it.
So it's terrible for the people involved, but not directly bad for society as a whole (but probably still bad in its second and third order consequences).