Imagine the following:
You are a new user with 1 rep. You want to ask a question about a manga/anime, that has no tag yet (in my example: Chaos;Head, tag would be chaos-head). How should such a user tag the question? He can't use the tag for the manga/anime, because it doesn't exist yet/he can't create it, he can't ask at meta or in the chat, because he hasn't enough rep yet and he can't use a generic tag like anime, because they're blocked. What should the new user do?
Should new users have the possibility to create new tags for new series? I think that's a bad idea, but it's the only one I could think of.