Using the [programming] tag is discouraged on stackoverflow.
Using the [apple] tag is discouraged on apple.se.
Using the [english] tag is discouraged on english.se.
For the above cases, the theory is that each particular tag should apply to every question on the site—that is, if there's a question where it doesn't apply, that question probably isn't a good fit for the site in general.
In the spirit of the above, is there a reason for the [writing] tag here?
It seems like, if we follow the logic as you've laid it out, there is no reason for the [writing] tag to be used here. That seems logical to me, if it's on this site is be default about writing.
I would tend to agree, as well. Every question on here is about writing in some way, shape, or form. It's too tempting for people to just select "Writing" as a tag and move on - which is incredibly unhelpful. I would like to see more specific tags used.
Just to play Devil's Advocate, I can see one use of the writing tag.
New users cannot create new tags, but also cannot post a question unless it has at least one tag. The writing tag could be a useful placeholder until a higher-rep user comes along and re-tags the question with something more relevant and specific.
Not that I necessarily agree with this, but it's good to develop all sides of the argument.
