For one, there's a lot of mythology about it. If there's anything less understood by the public at large than being a black belt, I'm not sure what it is. There're a lot of reasons for it, many of which, I'm sorry to say, have been promulgated by black belts themselves, either to impress their friends, or generate business, or keep the mystical aspects of the martial arts in the public eye.
Part of the problem is that really, a black belt is just that. A black bit of cloth. It is, at best, an acknowledgement of a lot of hard work and training, and to be honest, a bit of a spiritual change. At worst, it's something that someone bought out of the back of a magazine, and is nothing more than an ego boost, a false history. In between is well, everything. It gets more complicated by the fact that there's no set standard. The requirements for a black belt vary from art to art, school to school, sometimes even from student to student. Some involve intensive final tests, physical, mental, even written. Others involve a teacher deciding that the student is ready, and simply awarding the belt. Almost all of them are as legitimate as the next. But you can't point at a certification program, a college curriculum and tell someone "that makes you a black belt". It's rather like catching air.
It doesn't give you super powers. I can't kill at a touch. I can't "focus my ki" and put my hand through a bank vault. Hell, I can't really do a cartwheel. What I have found over the years is that what a black belt made me was a highly trainable monkey. It showed the more senior belts that I'm willing to do the work, and put forth the effort to learn the stuff beyond the foundation. That's what all the work up to black belt was: Foundation. 226 or so techniques, 6 forms, board and bottle breaks, uncountable falls, multiple wrist fractures, a broken nose, and dislocated/broken fingers, and it was the foundation to get to where I have the understanding to start learning the art, not just the movements. In my particular style, it means I'm ready to learn the stuff that makes this more than dancing about in funny pyjamas.
It also means that my role in a class changed. Unlike the underbelts, who are there to learn, most of my duties involve teaching. The students range in age, (Literally), from 6 to 60, I'm teaching, 2-3 hours a day, 5 days a week. I pay to do this, by the way. My son is one of the students I help teach. I imagine it's interesting for him, as he doesn't get to just be another underbelt. I sometimes wish there was another school nearby he could go to, and not have me in the way. But then, I get to be there when he gets a new belt, and be one of the teachers who put the belt on him. So I figure, maybe it's not so bad. I pay for our tuition at the school, and I help teach him, and the other students. My own training fits in around theirs. When we have belt or stripe tests, I help run the tests. I get beat up in demos, I help clean up afterwards while people enjoy the potluck that follows demos. If it sounds like a low-ranking black belt does a lot of scut work, that would be correct. Rather than making you some uber-killing machine with all the powers of a Mortal Kombat hero, being a black belt is rather like being a new 2nd Lieutenant. While you occasionally get to give orders, the truth is, you spend more time taking them, and listening.
Getting to first lieutenant is rather harder. Underbelts have perhaps 15-30 techniques between belts, and one form, or hyung. From white to black belt, as I said earlier, there are 226 or so techniques, and six forms, one form per belt. You get there in stages. To get to 2nd-degree black belt is a bit different. There are no stages. A partial list involves 120+ techniques, 4-5 sparring sets, (with weapons and open hand), 1 open hand form, 3-4 weapons forms, and a few dozen things that can be best described as advanced studies of various strikes. On the average, once you learn that, you then test about ten or so times. If you're fast, it only takes two years.
Oh, that's on top of all the stuff you have to learn to get to black belt in the first place. Testing can take hours. 4-5 in some cases.
Why do I do this?
I can give all sorts of popular answers. I can recite all sorts of things. But honestly, I'll give the same reason I gave for why I started:
It seems like the thing to do
That's still the only answer I can give that's worth a crap.
Oh, why did I post this?
Because earlier today, after four hours of testing in two parts, as I'm laying there during the demo, with a belt wrapped around my neck and one arm, being dragged about, ribs sore, collarbones bruised, I look over at the underbelts, in particular the kids, for whom being a black belt is something magical, and think
Are you sure you want to be a black belt?