When a database goes down (Sybase), or when requests spike for whatever reason (September 11), the scalability of a system obviously comes into play, and pure HTML going out thru port 80 can mitigate that. Of course some applications and sites must be purely dynamic and utterly up to date, but in my case with this blog, I like the fact that you get a page back without causing database lookups.
[For what it's worth, I do use some Server Side Includes on this site, so I sort of lied about the page not being assembled at request time. But, it's a fact that database lookups do not happen when you come to this page and all of the SSI's are non-essential functionality. So, the essential content of this site is always available, and that's good.]