I believe that smart people are quiet because whatever is going on in their minds is far more interesting than the mundane conversations that people have like the latest TV shows, celebrities or the new consumer products.
I see two types of people. Those who can talk even if people are not listening (and that somehow builds an audience in time), and those who talk only if someone really wants to listen. In most discussions or arguments people keep repeating their argument, regardless of whether they understand the other side or the other side already gets what they are trying to say. There’s no progress. And that means no point in talking.
Smart people will prefer to be the listener. It’s fun to listen to people with different perspectives. Some of the very smart people just don’t like to talk.
There's a saying that really fits into the scenario here.
AN EMPTY BOTTLE MAKES THE LOUDEST NOISE
Speaking teaches you little or nothing. It is far more enlightening in both the short and long term to listen and watch. Also, softness and quietness are universally associated with personal security and personal pleasure.
It's easy to get wrapped up in the excitement of being around big talkers. They bring you in with their wild stories and their bold, enticing passion about the issues they're discussing. The problem is that they don't really know what they're talking about. They're too busy listening to themselves to hear what anyone else has to say.
Smart people patiently wait for other people to say what they need to say. They choose to open their ears rather than their mouths. The quietest people are the smartest people; the ones who talk less have the most brainpower.
Smart people are too busy thinking to talk.
Here are some of the traits of smart/quiet people:
They write and read more than they speak.
They have stronger brains because they take time to reflect.
They aren't loners. They are just too busy inside their heads to take time out for the shit that you and I have to deal with.
They choose their words wisely.
They don't blabber; they listen.