Some riders avoid the handbrakes because they feel that they become too dependant on them. While there are many brake-users that feel they have found the right balance, there are also many who haven't. It's very easy to get accustomed to squeezing down on the brakes in order to

There are other riders that use brakes as beginners in order to learn the basics. This might be helpful to some but it's more of a matter of how you view mountainboarding. If you see it as what the ninety percent see it as, then you might argue that the basics of mountainboarding start with the fact that brakes are not part of the package. To them it's like fishing in a fish tank- where's the sport in that.
Still there are others who feel that by attatching a brake to their board they lose a certain element of style. Having to battle with the cable as you crash through low brush or drop your stance. They feel that it robs them of the simplicity, the flow, and the thrill of the ride.
There are many reasons why the ninety percent choose to say "no," to brakes. In the end, it seems they just want to feel free. There's something inside that tells them to let go and to ride hard. It's not a wreckless death wish, it's more of a plea from the soul to find oneself. There's a very unique thrill to be found in depending on your skills and your instinct alone as you ride. Decide for yourself.