Temperament

The difference between introverts and extroverts is that of temperament.

 That may offer some helpful insight to the difference between the need for solitude vs. the need for constant social interaction. Introverts require more reflection/thinking time and less socialization while extroverts require more socialization and less reflection/thinking time. Introverts occasionally become thirsty for human contact. But they become full easily. In order to recharge, they need solitude. Extroverts occasionally become thirsty for ideas and solitude. But they become full very easily and need human contact, socialization and the outside world to recharge.