Here's a theory: Extroversion is glorified and made socially mandatory because it sells. Extroversion, especially in the context of social media, promotes lifestyles and associated products and services, while introversion, by contrast, has no market value. If you're not extolling the virtues of your favorite snack food illustrated by a selfie of you snarfing it down, you are of no value to the retailer or the economy.

Extroversion, especially amplified and hyper-distributed by social media networks, is a valued market asset and money makes the world go round. Remember that the primary underlying function of each step of mass media development, from newspapers to radio to television to movies to the internet, is the advertising and promotion of products.

Introverts are of no value in this system, so the system stigmatizes introversion and glorifies and insists on extroversion to serve its purposes. In Oliver Stone's film JFK, Donald Sutherland's X told Kevin Costner's Jim Garrity that the primary organizing principle of any society is to wage war. I don't disagree, but the secondary organizing principle of any society is to facilitate commerce. Introversion is bad for commerce.