Presuming that you aren't the type of person who spends all their time out in public giving talks or something, how are you expecting people to "discover" you? By chasing links from your work? By just bumping into you in the grocery store?
I'm pretty sure I'm a worthwhile human being, but, y'know, I'd like to have friends, and I'd especially like to have friends that share interests with me, and are doing interesting things themselves. And I don't live in a place where those type of people are. So it'd be great if those friends found me... probably through the Internet. And how do I encourage that to happen? Well...
(None of which is to say that there's any reason to consume social media. Only to publish to it. Though that creates a funny Nash equilibrium...)