Why doesn't "Use Email Notification By Default" work?

I have this turned on in my profile, yet I still have to remember to turn on email notification when I post a followup article. Why? (I just noticed that it’s already on in this post, so maybe just a problem with replies.)

It doesn’t work from the quick reply box. However, if you go to the “post reply” screen (or use the quote button), it should be on.

Did you read the FAQ on that subject?

Sorry, I missed the FAQ.