User blog comment:SeraphLucifer/Discussion/@comment-79.115.74.88-20151118180644/@comment-9249716-20151118181657

No one really knows except the writers, and they may not really know how to reconcile it except to use it as a plot device for why he can't get to the boys. A friend and I discussed that his wings could've been damaged when metatron used it in that spell to cast the Angels out of heaven. We've also said that while there were Angels in heaven, there were still Angels on earth who couldn't/shouldn't be affected because they weren't in heaven. Castiel, who knows. It's likely to be some bs reason if the writers were to actually explain it.