This is where the system is all wrong. If a student can ace all the tests without doing the homework, then he doesn't need to do the homework. But unless he plays by the rules and does it, he fails.
As a kid who fit this mold to a 'T' all throughout my school years, I am going to respectfully disagree. I would routinely get 99s and 100s on tests, do zero homework, and get a 'D' or 'C' in the class...and I told myself the exact same thing: Why should I have to do the homework if I already know the info?
I can tell you that doing the homework prepares you for lots of types of jobs going forward...jobs wherein you have big projects made up of many tiny steps that need to be done, steps that cannot afford to be skipped just because we assume we already know the best way to get it done. Doing homework, while occasionally monotonous and pointless, teaches us that we aren't allowed a different set of rules just because we're smarter than our peers....we still have to do all the legwork.
I mean, I've had lots of jobs, and plenty of them involved doing work that I thought was pointless, and lame, and beneath me, but making sure that you cross all those t's and dot those i's is good for kids like that, trust me.
You know when it really began to hit me? Large scale research papers in my senior year of high school and college. Projects where one must do all the necessary 'little' steps along the way or else you end up with a bad product at the end. From what you've said, your son sounds an awful lot like me at his age, even down to being in JROTC.
There is an element of procrastination at play here, a little bit of perfectionism, and maybe a little bit of ADD, who knows. On my end there certainly was....I'm not hyperactive, but I cannot pay attention for the life of me to minute tasks.
For me, a large part of the issue was that big projects seemed large and insurmountable....and I had no idea how to get organized and where to get started. My advice is to really hunker down with him and focus on some goal setting exercises. Teach him (or have him taught) how to break a big project down to it's smallest component parts, and to assign deadlines to each one. It's worked wonders for me in my adult years, I just wish I hadn't waited so long to learn it as a skill. It makes it a series of small, manageable tasks as opposed to a huge, surly one.