Some designers are not PR machines, or don't really care about recording thoughts, some just lower their heads and work, and when it's all said and done they may not have anything they are compelled to write about. There is a difference between a good/great designer and a popular one.
I'm not saying that having a blog makes you an "accomplished author" as the original commentator suggests I was implying, I'm just saying that seeing your work is the easiest/only way to screen for talent.
