Board Thread:Questions and Answers/@comment-9826910-20130618064245/@comment-10710678-20130627132027

Ichigo was never given a true Zanpakuto, his reaitsu simply manifested into a large Katana-like spirit weapon much like how quincies manifest their own weapons using Reishi. So he was never given a blank Zanpakuto spirit, an Asauchi, which all Shinigami are given when they're introduced into the Gotei 13. Meaning he could never truly use his full Shinigami powers and his Quincy heritage could overpower his complete potential. Now that he has an actual Asauchi, Hollow Ichigo can imprint onto it and fulfill it's purpose.