Their job is to try and place you within the armed services. They are going to be persistent because it is precisely what they are supposed to be.
Consider how it is in the civilian world. You apply for a job. Maybe you hear back about your application/resume being read/trashed, maybe you don't. Then you get a call back from one company out of five you applied to, and then after a single scheduling conflict/change, everything kind of evaporates into thin air.
Even employment agencies lose people in the system. Where I work, we are starving for manpower and have two employment agencies trying to feed our lines. Since I work right near the entrance they are all told to meet at, I see countless numbers of them showing up at the wrong time, showing up for a tour with an agent who wasn't informed they were coming, etc. Because I come from the military - I take it upon myself to try and look after those people and make sure someone gets into contact with them about what is going on. I've been that guy lost in the system a couple times, and I'm not going to let it be other people if I can keep it from happening.
My point is - military recruiters are about the only people who are actually going to try and hunt you down for a job unless you are some person with patents or uber skillz/feats that some business research firm has compiled into a dossier for head-hunters to try and poach you from one business to the next (this is highly unlikely to be the case, and hasn't really been so for the past two decades - the employment market is heating up, though, and many of the same labor/skill pools are coming into heavy industry contest). You're literally complaining about an organization that is effectively trying to help you fill out your application and get you signed up for a part-time job that asks one weekend a month and two weeks out of the year.
Granted, you're young and don't have a whole lot of job hunting experience - but I can tell you from experience that the military is one of the few organizations that will hire a person based on aptitude and pay for their training up-front. Most businesses want experienced and/or prior-educated individuals to train on the specific platform. Few will look at you and go: "Huh, you seem to have a good aptitude for mechanical skills, we'll teach you how to be a machinist and welder!" Some will, once you're already in the fold and an employee of theirs.
