Personally I think (as Ozme does) that it's because dominants naturally tend to be more confident, and are less likely to admit that they too need guidance and training (perhaps more than subs, in reality).
Subs potentially chat more to blow off steam, perhaps. Not to say they get stressed as if they have a job, but because it can generate some intense personal feelings that otherwise can only be shared with their dom. And who doesn't like the occasional chat with like-minded people?