As a society we need people to be sociable and work together in order to survive. If people fall outside this criteria, they are stigmatized, because our reptilian brains surmise that they are less productive in aiding our survival.

We all know that extroversion and introversion are perceived very differently. We can talk until the cows come home about just being different, but of course the reality is that people are often goaded, nee forced, into being more sociable than they would like or stigmatized if they are their own person (and therefore go against the tribe).

Everything is dictated to by our need to survive, whether we realise it or not.