I am an introvert who masquerades as an extrovert fairly well most of the time. There is, of course, nothing at all wrong with taking joy and comfort in being alone. However, it turns out that a lot of the factors which are correlated with happiness (the article points at love/relationship satisfaction and work satisfaction, for example) are easier to improve when adopting some of the skills and habits associated with extroversion. That doesn't mean learning to enjoy going to the club every night; it means learning how to make very good first impressions and getting along well with co-workers. If an introverted person is already satisfied with their life, then of course they don't "need" to be comfortable with social company, but this article seems to be written for people who are not as satisfied as they could be.