While I find that WYSIWYG editors have their place, I could not stand to not do most of my design in code. Some of the benifits of this include:
No platform/software dependance. I create my pages on multiple platforms, sometime other people's computers. If I used my computer only, I may find that I liked WYSIWYG enough to use it regularly, but as I use other people's computers quite a bit, I need to do my design in a way that if familiar to me on all platforms. While various text editors have their differences, they all operate closely enough that I can sit down at any computer and create something.
Better standards compliance. I make sure that everything I create validates and uses structural markup. While this is possible in some visual editors, it is far more difficult that just knowing the code. And as I do much of my design work (95% or more) in CSS, I need the flexibility that hand coding offers.
Easier server side programming. I do quite a bit of server side programming. It may be more than I need, as I am fairly new to it, but even if it was just a little, visual design tools make it difficult to do any of it, much less
echo items (such as table rows and cells) in loops.
Better understanding of markup. Part of using standard markup is understanding that it is not meant as a visual design tool. Using WYSIWYG editors gets people in the mindset that, for instance,
<h1> tags mean "big and bold", rather than the main title of a page. They enforce the misconception that (X)HTML is meant for page layout, rather than describing what all the parts on a page mean in relation to one another. Understanding this is the key to creating useable, accessible, and interoperable web pages.
On the other hand, I'm not going to lie and say that I never use visual editors. I do so rarely, and never on a final product, but I find that using Claris Home Page (extinct for several years now, but almost supports HTML 2.0) to clean up documents, create headings, and the such on existing documents can be faster than using a text editor.
I don't believe that anyone even semi-experienced in web design should even remotely depend on them, but they can be quite useful for newbies. Not for creating pages, per se, but they let new users create a page then examine the source (hopefully after running HTML Tidy on it) to develop a feel for how the code works. That is part of how I learned.
Summarized: visual editors have their place, but for the ultimate in power and flexibility, nothing beats working with code.