According to your rationale, WP shouldn’t have the Codex either; but you know what? IT’S THERE FOR GOOD REASONS
Yes, WordPress does have a codex, but do you think it was all written by the authors of WordPress? Nope. Anyone with an account can log in and update the codex, expand on some of the content, or even fill in some of he blank pages.
That’s the beuty of the Open Source model – Anyone can contribute. If you think that documentation is missing or incomplete or something, there’s nothing stopping you from writing it and contributing. In many cases the auuthor would prefer that to a small monetary donation!
And I expect you’ll probably respond by saying you couldn’t even help write the documentation as you don’t understand how it should work (despite others saying it’s intuitive). In that case, you could still help by being specific with what you’re struggling with.
Had you started this thread by saying “How do I make it do X, I’ve tried Y and Z and they’ve not done quite what I expected because…” you would have got a much quicker respponse, and one that hellped with what you wanted.