You're confusing things, Yahtzee. Companies just want money. They add multiplayer and co-op to everything because it's "social", because as Facebook taught us, we live in the "social" age now, which is "modern" and "revolutionary" and, above else, makes a fuckload of money. And fuckloads of money the developers need, for we live in a time of great insecurity and fear, where games cost human souls to make and need to turn even bigger a profit. Sure, some devs care less about the money and more about gaming "becoming relevant" and "evolving", because they're morons who honestly believe that this is the way to go.
Multiplayer/co-op elements are just an extension of "broadening appeal", for everyone these days seems to think that the more people get in on something, the better, ignoring the fact that the masses at large are, indeed, shit. Jim was right with his episode this week, and it pertains to this as well. Everyone truly is desperate for attention.
It's not the people who ask for this shit, it's the ones making the products. And they don't care if you stay introverted or not. They only care about leeching off the people who are actually social.
Also, ads don't show people drinking alone because it obviously carries depressing undertones. Other than that, though, I sympathize with the rest you say about society shunning introverts. What would you honestly expect, though?