I don't think it's necessary to be an extrovert per se. Networking is important as that is what helps you create opportunities, if an actor is able to bag the right projects and is able to win the audience's hearts then doesn't matter if he ain't all over. Few appearances during the movie can do the job. Anyway, all of this is a recent phenomenon I guess. Earlier the promotions weren't too much. Stars antics were visible only during award shows and their personal lives were known to us via print interviews. It was better. Overdose of these stars outside the realm of movies is kinda annoying.
However, I can't deny that creating an aura of oneself off screen does help at times. Like Ranveer has created a strong fan base with his off screen behavior. Alia too, greatly used the social network to create an adorable, cute image for herself. Whereas people like Shraddha are hardly visible on social media, yet created a place and a fan-base for themselves. So basically, my point is ...all these are different means to promote and market yourself. Different approach for different actors.
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