Some people like the BB in Final Fantasy, but most people recognize that it is a stupid character.
Yeah, it's cheap, but the actual fun of the game, the part where you strive to acquire the better weapons and learn the best magics, kind of like Del Murder was saying, is missing. The BB just gets stronger. Then it lives or dies. Whatever.
It is a boring class with no diversity. By is I mean was, of course.
In order to provide diversity and purpose, the designers had to give it more than just powerful knuckles. Healing is cool. Use some sort of zen ying/yang concept to justify a mystical mind-power sort of thing.

A better idea might've been to eliminate monk classes and stick to swords and sorcery, but then it wouldn't directly imitate D&D, and something might feel missing. The truth is that the true identity of the monk is both an anomaly and a freebie. Anybody can do anything with it, as long as it's somehow different from a red mage that can't swing an axe.