Hopefully this hasn't been pointed out already... Often times introverted people are brimming (if not full) of empathy, and compassion. The joy they give is t

Hopefully this hasn't been pointed out already... Often times introverted people are brimming (if not full) of empathy, and compassion. The joy they give is the joy they receive. That reward system is personal, internal, and can even be sullied by outside observance. These people (whom you might have known, or know now) really don't need compliments. In fact, compliments border on uncomfortable. They probably give anonymously. They put themselves in peoples shoes and embody their difficulty. Their reward is to help because that effort returns to them in an unspoken and even unnoticed joy. Having friends, or a social network is definitely a way to create opportunities. But for some people, that isn't necessarily worth the engagement. A very empathetic person might not want to loosely couple themselves in a social network with anyone else if they feel like they won't be able to offer their finest. It'd be unfair. They don't need those connections to find joy. They generate their own in compassion.