User blog comment:Xilinoc/Ch. 552 - The Fundamental Virulence/@comment-4509522-20131010132123/@comment-11051098-20131014233046

I haven't read such, but they might want to see how far the Gotei 13 can go on their own, without help. After all, the purpose of the Royal Guard is to protect the Soul King.

But then, if the Gotei 13 are overrun and on the verge of defeat, the RG cannot sit back and let it happen when the Wandenreich wants to destroy the entire world.

Also, I don't think Kubo brought them into the story just for show, just to be there and offer some help and healing and that's it. I think at least some of the RG-members will fight.