User blog comment:Xilinoc/Ch. 573 (Let Unohana return plz)/@comment-5405150-20140324171650/@comment-1759748-20140324235803

Actually, Byakuya coming back would only have had repercussions on the fanbase. Kubo had fully intended to kill him off until complaints and most likely threats from angry fangirls changed his mind. Same reason Toshiro isn't dead. It's because Kubo is just like Toriyama: Unable to end a character because of the "fans".