Why your blog should be static by default
Most blogs are read thousands of times for every time they are edited. Rendering the page once, at publish time, and serving that file to everyone is the obvious win.
Speed
A static page is a file. A CDN can serve it from a city near the reader in a few milliseconds, with no database query on the way.
Security
There is no plugin code running for each visitor, so there is very little to attack. The admin panel lives on a separate, private address.
Render once, serve a million times.
Dynamic parts such as comments, search or paywalls can still be added as small islands on top of the static page.