It would be interesting to see how many of the remaining 23% are in the slice of society where a military career makes financial sense. When I joined the Army I was going from having been fired from McD's last month to making $1K a month with food and shelter taken care of. That made sense at the time. My kid is plenty skinny, mentally stable, and drug free, but he's also a successful college student and budding entrepreneur, so he's not going to be wearing a uniform unless we go full WW3 conscription.
I was speaking with an advertiser who was somehow involved in the return of "Be All You Can Be".
He stated that military recruitment is highly sensitive to unemployment rates. Unemployment is very low now, especially for entry level and service roles that would hire an unskilled 18 year old.