Adding a bit to the other side of the equation, I think extraversion and introversion are independent spectrums. The 'introverts get energy from being alone, extraverts get energy from social interactions" explanation implies that introverts can function as hermits in total isolation and extraverts have no need for 'me time'; this is not my experience. Almost everyone has some baseline social needs that need to be met, and almost everyone needs some quantity of time alone.