What? So there's no added security by using TouchID as some here seem to think? So it's a pure convenience thing ... if so then well, I'm personally not very annoyed by having to enter my password when my hands are on the keyboard anyway.
I think the idea is that you can choose a very long and complex password, because you won't have to enter it so often once you enable TouchID. Without TouchID, most people are tempted to choose passwords that are easy and quick to type.