Group owners might decide in the future to use Special Messages.
For 17 years on Yahoo!Groups, our group never had Special Messages. It wasn't policy; there just was no reason to send any. And then there was. So we sent Special Messages. I hope they reached the people who chose that option.
I think there is no harm in letting members choose "Special Notices Only" even if they never ever happen. Without that option, their only choice is "No Email" which does nearly the same thing except that it prevents them from seeing a message when it really is important.
