Apparantly the reason is because the Japanese would tend to get offended by the character in X show having something "unintended" come out of their mouths, hence why sometimes we have outtakes NOT set to picture if at all.
Not quite. According to the guys who licensed Takeshi's Castle from Beat Takeshi and turned it into MXC on Spike TV, Beat Takeshi gave them permission to screw around with the dialogue all they wanted and even went on to say that if he were to license an American show, he would do the exact same thing. Then again, that may just be Beat Takeshi and not all of the Japanese entertainment industry as a whole.