Because real life is full of dichotomies, and they are not all false. They even exist in our profession -- we call them "engineering tradeoffs".
Have you seen many "fancy-ass websites" with great essay content?
Perhaps you can find 1 or 2. I doubt you can find 10. There's a reason for that too. Most of the good writers I've read value simplicity, both in their writing and in their presentation. And, as they believe in the value of their content, they see no need to dress it on a "fancy-ass website".
That's what the whole "content first" / "minimalism" etc movement has been all about, from the 37 Signals blog to the emergence in our community of stuff like Jekyll.
And I don't see what the fancy-assness of the website would add to PG's essays. Care to enlighten me?