User blog comment:Xilinoc/Ch. 572 (inb4 "Kenpachi doesn't have Shikai")/@comment-1351982-20140312125723/@comment-1351982-20140312142118

Another reason is that Kubo has sort of a pattern that when a character, who plays even a remotely integrally part of the story, they usually die with someone that cared about them or was important to their character arc. Examples Gin died after Rangiku found him, Nel was there when Kenpachi killed Nnoitra, Masaki died near Ichigo, and Tosen died after being forgiven by Sajin and Shuhei. I doubt Kubo would change this narrative style after 13 years.