Many hiring managers look for the ability to write HTML from scratch not because it is faster, but often because it shows that the developer has the ability to go beyond tools to create their pages. If you know how to write HTML from scratch, you can always move to an editor, but it's very difficult to move from an editor to straight coding.
Knowing HTML can allow you to make changes faster than someone who writes with an editor. For example, at my company, I work directly on the Web server and when I find an error I just go straight into the HTML, make the change, and save the file. My coworkers who use editors would have to download the file to their hard drive, open it in their editor, make the change, save the file, and re-upload it to the server. Most of the time, that type of time difference won't make a difference, but that one time it does, I'm glad that I can access the HTML.
Knowing HTML will also allow you to correct errors that WYSIWYG editors might add to the code. Some editors add strange tags and attributes that can cause less compliant browsers to choke. And sometimes you can get the exact effect you're looking for more easily by writing the HTML by hand.
