User blog comment:Mrlmm0605/Let's Talk Bleach!: Part 11- Kenpachi Zaraki/@comment-26091912-20160401095757/@comment-24531362-20160401110015

I would argue that, as a result of power-creep that is expected in any action-fighting show, Kenpachi had to remove his eyepatch in any meaningful fight beyond Ichigo, and had to release his Shikai in any meaningful fight beyond Gremmy. Important opponents are expected by the narrative to be stronger than the previous one (unless the protagonist is weaker, a la Fullbring Ichigo), so powers necessary to match the weaker foe would be necessary to battle the stronger one. That, at least, is the narrative need. Kenpachi's dubious upper limits make this questionable in-universe, but the story demands it.