The Good Conduct Medal is one of the easiest medals an enlisted troop can earn. It's an award given to enlisted personnel for every three years of "honorable and faithful service." During times of war, the GCM can given out at one year of good service and can be posthumously awarded to service members killed in the line of duty.
But the GCM isn't the same as a service stripe, which is given to soldiers every three years, Marines, sailors, and Coast Guardsmen every four years, and is never given to airmen. To earn a GCM, you need to keep your nose clean (or don't get caught doing something you shouldn't) for three years. If you're a solider, boom, that's an instant 10 promotion points.
The intent behind the GCM is to award outstanding troops who've managed to go three years without ever failing to be at the right place, at the right time, in the right uniform. The disqualifying factor for this medal is if you ever receive an NJP.
Now, what is and isn't considered eligible for a non-judicial punishment is loosely defined and is entirely at the discretion of the commander. Talking too severely to a subordinate could be considered an NJP-worthy offense by a commander that's cracking down on hazing, while another unit's commander may turn a blind eye to horrendous acts that discredit the military.
The moment a troop gets a "Ninja Punch," their 3-year GCM timer restarts. Three years after a sergeant knifehands a private, that private is once again eligible for a Good Conduct Medal. A scumbag who has brown-nosed the commander or has a commander who "doesn't want the unit to look bad" will receive this medal every third anniversary of their enlistment. Do you see the discrepancy?
Once again, one unit may make an elaborate ceremony to honor the troop for their three years of good conduct while another may just ask a troop to buy a Good Conduct Knot to add to their ribbon rack. Again, this is at a commander's discretion.
There is a silver lining to all of this. Fresh young troops who are giving the military their best can feel like their world's been shattered the first time they screw up. Stern talking-tos and regular bad conduct counseling statements don't blemish one's good conduct streak — take the lickings and move on. An offense typically only turns into an NJP when it's one in a series of misconduct.
The Good Conduct Medal should be awarded to those troops who exemplify the military values. It is a flawed system that sees undeserving scumbags awarded while good troops who make a genuine and innocent mistake aren't — but the troops that do deserve it and earn it make the military proud.