Simple: do you want to see more August Celestial's lore?
There are just so many questions.
Were they around when the Mogu enslaved the other races of Pandaria?
If they were, why didn't they help the slaves?
If they decided they should let the mortals save themselves, then why did the Celestial's help Golden Lotus at the end of the Golden Lotus story line?
Why didn't they act against the Mantid before the Sha infected them? They were a blatant threat, trying to break through the wall.
Yes, I'd love to see more lore for them, but the best part is that they are so mysterious, it just makes you guess.
Edit: I'll be gone for 5-6 hours as of this edit. Feel free to keep discussing if yall want to.