There's a school of thought in change management that suggests that a time comes when current stories aren't working for the culture you're trying to move an organisation towards. A few here have said morale was low at FB right then.
At times like that, restating some important old stories and legends, salted with some useful new ones can help to galvanize people and create the culture change you want.
A good example is someone mentioned in this thread is Zuck's beat up old car. That's a great old story for the early days, but probably needed burying at the Red Book time. Clearly he's not going to drive that forever, so you need some more up to date motivational culture lore which embraces more excess while retaining how the Devs are still world-changing hackers who should work all nighters because 'we're all in this together for mankind, team'.
The car wasn't beat up (I don't see anyone claiming that here) or even all that old... it was just a very modestly-priced choice of vehicle for someone of Zuckerberg's wealth and position. I believe he was still driving it at the time of the red book.
Nor does the book really "embrace more excess" financially, at least as far as I can remember (and I don't see any of that flipping through my dusty copy briefly just now either). Instead it's the opposite: "Facebook was not originally created to be a company", "We don't build services to make money, we make money to build better services", etc.
Again, this was a period of disappointing post-IPO stock performance. The market wasn't convinced yet that FB could successfully transition to focusing on mobile. It took about 15 months after the IPO for the share price to start looking more positive.
So that was a factor, combined with an obvious desire to keep aspects of "chaotic small nimble startup" vibe/culture at a company that was definitely no longer a startup.
At times like that, restating some important old stories and legends, salted with some useful new ones can help to galvanize people and create the culture change you want.
A good example is someone mentioned in this thread is Zuck's beat up old car. That's a great old story for the early days, but probably needed burying at the Red Book time. Clearly he's not going to drive that forever, so you need some more up to date motivational culture lore which embraces more excess while retaining how the Devs are still world-changing hackers who should work all nighters because 'we're all in this together for mankind, team'.