Because it's a social game (i.e., you can't play alone), registering is more of a quality control than anything, like news.ycombinator, for example. Registration is extremely minimal (email address only required).
Once I did complete registration, I was not logged in - why not? Instead you showed me a "2. Player Information" screen where I had to read about clicking a "home page" link (not underlined, similar color to the rest of the text, tiny font), and then log in again.
Take a look at the Tumblr signup page.
I'm motivated because I've read the book, but most people wouldn't bother jumping through all the hoops.
Good luck with the game.