User blog comment:Njalm2/Nanja's Point of View: Shinigami Edition/@comment-1493741-20150503073419/@comment-5651818-20150504014632

Great, now you guys don' turned Sei into a Hippie. Better break out the Bongs.

Anyway, the way I see it, Shinigami are a form of Spiritual Evolution from that of Humans. As Sei said, Reiatsu can be too strenuous to be used by a Human whether in Kishi or in Reishi form. Just as there is a limit to how much Reiryoku the human body can contain. So, maybe the Shinigami are relieved from the weaknesses and limitations of their former existence (still Human at the core, but now with a much better and more refined surface).

That's just my two cents. Let me know if you want me to explain it a bit more.