In my opinion, a hubber IS a writer.
I think anyone who uses the written form, literary arts if you will, is a writer. Writers include technical writers, newspaper reporters, authors, bloggers, reviewers, academic research writers, and many, many more.
Just like some writers write for their own intrinsic gratification, so do some hubbers. Other writers write articles for magazines strictly for monetary compensation, as do some hubbers.
Some of the hubbers here use this merely as an outlet for their artistic expression, such as the poetry hubbers.
That being said, some hubbers aren't very good writers. You'll notice that a large number of hubs are absolutely horrible both grammatically, stylistically, and in content.