User blog comment:LexFacie/Thoughts about Bankais./@comment-24460247-20140711022059

As stated by Urahara and Mayuri about quincy's not being able to steal resurrections of arrancars its the same thing for ichigo because his mother was attacked by the "white" (One of Aizens hougyoku experiments) and that piece became apart of ichigo's power so thats why quincy's are unable to steal his bankai.