a) You have a career that requires some PR management
b) You're the type who gets pleasure in showing off (the best image of) yourself to others
c) You are bored, and you get a small thrill from the attention
Are there any other reasons to be a regular, active participant on Twitter, Instagram, or Facebook? I get 'just having one' as a sort of contact directory, but beyond that...
Would an educated, independent thinker, someone who really tries to engage and understand the world and has discovered interesting opportunities which they pursue, really have any reason to spend significant time on social media?