Of course you don't have to be, but what if you want to be? You don't have to go to Hollywood with the goal of being the next Tom Cruise or Will Smith or Angelina Jolie... you could act in obscurity anywhere, pleasing a core group of fans who are lucky enough to see you in action at your local theater. But if your aspirations are bigger -- if you want to be famous and use your fame to connect with as many people as possible through your chosen medium (like film or social media), what's wrong with that?
Of course you don't have to be social media famous ... but if you want to be, then go for it. I don't see any reason to listen to someone telling you not to pursue your goal just because it's not an imperative for everyone who uses that medium.