Many of them could, in fact, stop being vocal. They did not have an incentive to. They had an incentive to be/become vocal. That's the fundamental issue which

Many of them could, in fact, stop being vocal. They did not have an incentive to. They had an incentive to be/become vocal. That's the fundamental issue which has very little to do with extraversion. The world rewards loudness, and most attempts at making the world slower and more silent are actively thwarted.