|Because Word Bearers are boss.|
Now Chaos Space Marines were my first army, and I'm definitely excited for the new codex. I mean, I've been waiting 2 years to have a book actually worthy of Chaos, and it finally looks like it's here, but I'm not going to build myself an entire new Chaos Lord or order any of the new models until I actually have the book and have mostly worked out my army list. Who wants to kit their Lord wrong and find that they've got to either got to play with him how he is, not happy with how he perfoms in game, or have to wreck your nice paint job removing the incorrect parts and replacing them with what he should have? I certainly don't.
This is a damn expensive hobby, and I for one am not wasting any cash on anything I don't plan on playing with, nor am I going to paint up a model to find that I don't want to use him as is. I think doing up generic CSM squads or Terminators or whatever is fine, because those are some pretty safe options, but I definitely don't think you should be ordering too many toys or building any new Lords just yet.