Those with criminal records have often opted for the military as a way of life. In the past, judges would even "sentence" youthful offenders to "jail or the Army." When I was in Basic Training it was a standard joke.

Can't say for sure how often it happened, although I suspect that it happened more often than we care to think about -- you know, "a good dose of military discipline'll straighten the boy right out!"

Funny thing -- turned out the military didn't want them either. Far too many caused as much trouble for the Armed Services as they did for their local cops. For some time now recruiters who "enlist" too many (some always get through, but get caught further along) face rather tough prospects, from reprimands to (even!) prison time (although I don't know of anyone who's been sentenced, but it's on the books). Yes, sometimes it did "straighten out" the "punk kid" but all too often it simply added to the military's problems.

Criminals, by and large, don't have the self-discipline necessary to survive (and allow others to survive) in combat.