Why did he leave the service?
Somewhere around 14 - 16 years in the service member takes (I hope he did) a hard look at their life.
4 to 6 more years of the samo-samo to hit 20 and retire. A little older, no assets and no firm job offer but his retired pay.
Or get out now while a little younger, no retired pay but a chance to get a better paying job.
He pulled the trigger and missed.