It's a stereotype--many of us are introverted because our inner lives are so rich we don't need to look outside our own minds for entertainment/stimulation.
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"Ego non immanis, sed mea immanis telum." ~ Ares, God of War
(Note to Moderators: my warning number is wrong on my profile but apparently can't be fixed so I will note here that it is actually 2, not 3--the warning issued to me on Aug 20 2016 was a mistake but I've been told it can't be removed.)