User blog comment:StonerCatJay/Rereading the series- theories and speculation/@comment-3230060-20140523145720/@comment-24963493-20140524054251

I hadn't thought about that. I think that it was mainly because he didn't want to lose control of himself (and potentially hurt an ally because of his inner hollow) but that fear could have gone to irrational levels and affected him more because he's a Quincy.

I never really associated the rain in Ichigo's inner spirit world to be because of his inner hollow. It was more because it meant Ichigo was upset/sad/beat down/etc., and the Old Man only wanted to protect Ichigo. There had been rain within Ichigo's inner world before, sometimes because of feeling hopeless against his inner hollow, sometimes for other reasons.

That's definitely a possibility. Again, not something I've thought too much about, but it also could have been foreshadowing about Yhwach's restorative powers, and how he's practically (if not completely, as long as he isn't killed) immortal.