I get that. There are two distinctions between "any other job" and military service, which I think matter, and I'll get to.
But, you're also not wrong. If I say you're not old enough to sign up for the service, I'm also saying you're also not old enough to say get a loan for $40,000 of tuition without so much as a credit check. I'm less appalled at military recruiters on high school campuses, and more appalled at the weird magic we all believe happens at 12am on everyone's 18th birthday. Like, yesterday, you were too immature to sign a lease, or buy a rifle, or vote, and you should 100% listen to people in authority, because they know what's best, but today, you're more than mature enough to take on every shred of responsibility for all the things you are legally entitled to, and if any of those people in authority take advantage of you for their own selfish ends, it's at least 50% your fault for what happens to you.
I do draw a distinction between serving in the military and any other job for 2 reasons. First is the obvious. There are very few, vanishingly few, civilian jobs where you may be asked to take a life. Most police departments require that police be over 21, even. Second, there are very few, vanishingly few, civilian jobs where if you just up and decide one day that the job is not for you and quit, no-call-no-show, you go to jail, and permanently damage your ability to get any other job and certain kinds of government assistance, for the rest of your life. Its weird to me that we're just a-ok with (again) 18 year olds making that decision, given that we don't let them buy handguns or alcohol, or rent cars. We obviously, as a society, decided they lack the good judgement to make those kinds of decisions, and accept those kinds of responsibilities on their own.
What I'm saying is that buck privates getting ludicrous financing terms on a Dodge Charger from the dealer nearest the barracks is such a meme for a reason.
There's an argument that jobs which can take a life require more maturity, and there's been talk of specifically limiting jobs like infantry to older, more mature, and more physically-trained people.
That said, the vast majority of military jobs are not combat-coded. They involve mundane things like fixing aircraft, crewing ships, doing admin paperwork, moving boxes, and so on.
I want to be super clear here, I actually have no special objections to e.g. recruiting in high schools for college ROTC programs. As you say, the goal is to produce an effective officer at the other end of years of development, but also years of just maturing and growing up outside of the home. A good friend of mine actually separated from the Air Force (as a captain) and subsequently rejoined specifically to do that (as a stepping stone for getting a waiver to fly an A-10, but he was deemed just a little too colorblind for that, and so he resigned as a major), and it didn't seem at all problematic.
My issue is specifically with recruiters driving enlistment right out of high school, especially for jobs that don't have much of a civilian equivalent market. My friends the nuke techs, or the guy I knew who did something with missile controls on a guide missile cruiser were pretty much in the same spot as when they started, but with the GI bill (although only one of those three used it). The guy I knew from high school who deployed to Afghanistan got a Purple Heart and a Combat Lifesaver certificate, but not much else before he was old enough to buy a beer.
Yeah, its an important job, but its just a job, and we don't let Walmart try to drive applicants in 3rd period. If the steady diet of nationalism and militarism that kids get from age 3 on isn't enough to get them to join up, maybe we should rethink letting them interrupt Algebra 2 to dangle $50k in front of a bunch of 17 year olds.
But, you're also not wrong. If I say you're not old enough to sign up for the service, I'm also saying you're also not old enough to say get a loan for $40,000 of tuition without so much as a credit check. I'm less appalled at military recruiters on high school campuses, and more appalled at the weird magic we all believe happens at 12am on everyone's 18th birthday. Like, yesterday, you were too immature to sign a lease, or buy a rifle, or vote, and you should 100% listen to people in authority, because they know what's best, but today, you're more than mature enough to take on every shred of responsibility for all the things you are legally entitled to, and if any of those people in authority take advantage of you for their own selfish ends, it's at least 50% your fault for what happens to you.
I do draw a distinction between serving in the military and any other job for 2 reasons. First is the obvious. There are very few, vanishingly few, civilian jobs where you may be asked to take a life. Most police departments require that police be over 21, even. Second, there are very few, vanishingly few, civilian jobs where if you just up and decide one day that the job is not for you and quit, no-call-no-show, you go to jail, and permanently damage your ability to get any other job and certain kinds of government assistance, for the rest of your life. Its weird to me that we're just a-ok with (again) 18 year olds making that decision, given that we don't let them buy handguns or alcohol, or rent cars. We obviously, as a society, decided they lack the good judgement to make those kinds of decisions, and accept those kinds of responsibilities on their own.
What I'm saying is that buck privates getting ludicrous financing terms on a Dodge Charger from the dealer nearest the barracks is such a meme for a reason.