This is probably a matter of game mechanics, but you all might be able to answer it anyways.

There are basically two numbers that affect your offensive/defensive in this game. Your AMS and your DMS, right? If I understand correctly, the higher your AMS in relation to your weapon's main skill requirement (like if your hammer requires 150 2hb, and you have 100, etc.), the better a chance you have of doing more damage than you would if your skill was lower. Right again? I hope so, because if I am, and I have figured that correctly, then what I am thinking makes sense.

Basically, if my above statement is true, then crit buffs being MA self only makes sense. Essentially, everyone but MAs can overequip a weapon. I know, I know, nothing is stopping a martial artist from equipping a weapon the same as everyone else. But honestly, it's a waste of IP if you do. For the sake of argument, let's consider that a pure MA can't overequip the same way others can. Since an MA's fists have no main skill requirement like, say, a hammer, then our AMS will never have that "skill check" against our weapon requirement. Because of that, the chance to do more damage than normal (note, I'm NOT talking about a chance to crit. I'm talking about a chance to hit your max damage without a crit) will never increase like it would if an Enforcer cast challenger on him/herself. That's where crit buffs and all the damage modifiers MAs get come into play.

I hope that was all correct, because otherwise I made my head hurt for no reason. Someone let me know if you think this is right. I'm gonna cross post to other places too to see if anyone else knows.