They take you on when you are crippled, weak.
They know that, when you are vulnerable, they can mold you into the relentless warrior machine they want you to be. In the beginning, you can wear only black, in homage to the All Great, Ever-Seeing, All Powerful, All Knowing Overlord, Darth Vader, who was viciously murdered by his own brat, the traitorous Luke Skywalker, whose legions of rebels we have almost annihilated from the stars. All power to the memory of our Dark Lord Vader!
You are given one boot to start out with. The rest of the armor you must earn, one agonizing piece at a time. Being only given one boot to begin with, is pretty agonizing in itself, because, when they order you to march, you tend to go around in small circles, which makes you look like a fool in front of everyone. And, believe me, they are laughing themselves silly at you.
But slowly you harden up. That is how they want you. Hard enough to wrangle Banthas. Hard enough to take on Jedi scum who have integrated themselves into whatever society there is on whatever puny planet they have decided to hide out in and cling to like mosquitoes in a nudist colony. Hard enough to withstand an infestation of Trusolian leeches bigger than the gonads they attach them to and nourish themselves upon. Hard enough to hold off an attack of Monttomberan assassins, who attack by shooting Ramtiac sponges into your body that absorb all your vital fluids, making you wither slowly, until you look like King Tut's dehydrated mummy. Hard enough to withstand the humiliation of Dromdanian college punks, who wait until you are using the potty and have various sensitive bodily parts exposed to the outer world, and take pictures of you that they embarrassingly put on Facebook (foul, treacherous bastards!) Hard enough to …....ok, you get the idea already!
Time, and years of discipline, eventually bring you to the day where you receive your helmet, and you then become a totally anonymous, faceless entity forever, even when you are intimate with your wife, as you must wear the full body armor at all times. This might seem like asking too much, but we can't afford to have you making babies, as that would send our costs skyrocketing by having to support a bunch of useless rug rats, too. We have universes to conquer! We don't have time and money to spend on mere physical passions, and tiny people who can't even hold up a blaster!
This is the training of a Storm Trooper. It is hard, but it is not without rewards. If a limb is severed in battle, we will replace it with a prosthetic which will give us time to use you again until some enemy finally blows you away completely. After battles to take over major planets, you will be allotted one hour to scavenge through the debris to pick up souvenirs to send home, like busted-up blasters and half-malfunctioning droids searching for some guy named 'Obi', or scraps from the Millennium Falcon, that someone finally had the decent-enough eyesight to blast out of the sky (cripes, it only took 12 films to do it in!)
Yes, becoming a Storm Trooper is an arduous and dangerous process, and one that takes great will and perseverance. But it is not without its rewards. The insurance is good (as long as you sign the waiver stating that when you are finally blasted into eternity, what is left of your body can be harvested to make the building blocks of clones), and you do get college loans (as long as you major in something like 'The Talents of the Dark Side of the Force' and not something silly, like Art). Also, the bad girls really lay down for Storm Trooper guys, even if they never do get to see them without their helmets on!