People go to his site for the words, not for the site. A flashy design would be distracting, and for someone who (IMHO) writes as well as he does, anything that takes away from that is impractical.
It's the same reason he'll link to images or videos or sound clips, but he never posts them directly on his site.
But his writing is the same way -- he's gotten to the point where he spends more time sneeringly mocking Apple's detractors than fellating Apple.
He wrote a bunch a while back about how Apple needs an equivalent rival like Nikon/Canon. It would sure make his writing a lot more interesting -- they've now got a Dreamworks to their Pixar in Android, but that's just giving Gruber more insubstantiative shit to sling.
It's the same reason he'll link to images or videos or sound clips, but he never posts them directly on his site.