Talk:Sypha Belnades (animated series)/@comment-27533697-20180726013352/@comment-28192080-20180728191228

Sexism. A woman doing magic is a witch and must be burned. A man doing magic is a sage and must be respected.

Though I also suppose that hiding the identity comes first so nobody can track the individual down, so it's not so much as "dressing like a boy" as it is "dressing like nobody can tell who you are".