It's more like the universally accepted "right way of doing things" being taken a step further. Why should the system that generates the HTML be the same one that serves it?
The year 1994 called and would like to talk to you about your backward flowing sense of time and fads. :)
In all seriousness... when the Web was born (on Tim Berner-Lee's computer) it was pretty much just static HTML reached by HTTP. Then folks added static file generation, optionally, behind the scenes. Then techniques like CGI to make it dynamic each request, typically from a C program or Perl script. Anyway... Turns out, not all old ways are bad. For certain use cases, just plain HTML-over-HTTP, totally static, works fine. And hard to beat it's performance and resource usage.
But it seems like static site generators became a fad recently, like Rails a few years ago, and this makes me slightly skeptical. It's always suspicious when somebody claims there is only one right way to do something. When it comes to me, feel free to have a backend for your blog. This certainly has some advantages, just don't forget about performance.
Or just use a hosted service. TMTOWTDI.