Why? It seems pointless, a waste of time & valuable resources
And yet here you are, making an argument that's been made before, that didn't convince anybody when it was first raised, wasting valuable time posting here! It seems to me that if you were genuinely interested in learning the answers to the questions you pose you could ask yourself a fair few of them.
To answer your questions in general: It's a hobby. I enjoy having my ideas challenged and conceiving new rhetorical constructs, reading about bleeding edge science from the source and talking to people (who incidentally, do actually compose 'a community'). Winning an internet argument in a fatal coup of brilliance serves as a motivating factor (and a sort of unintelligent guiding force, a free education director if you will) in educating myself about the world I live in.
To really get to the heart of things
Edited by Modulous, : No reason given.