Don't bring me down
Designers have blogs for a number of reasons. Often they want to show off their portfolio, maybe to expound theory, or whatever tickles their fancy. But as designers are creationists, they often have the desire to recreate their vision for their web site. Take it all down and build it back up again!
The other thing that designers often want is some noteriety. It's not about being some A-list web celebrity but rather to be known for being a great designer. Blogs have been effective tools in spreading knowledge that can define oneself as an expert in ones field. But when a site is stripped of design AND content, only to be rebuilt anew, it destroys a very important relationship: that between you and the search engine.
Search engines love content, they eat it up. And that's what readers like, too. Having destroyed that relationship, you've made it harder for new readers to find your site. You make it harder for people to learn about that wealth of knowledge because it's gone.
Listen to your site, it's saying, "Don't bring me down!"
As a footnote, 60% of my traffic currently comes from search engines.