That's entirely different than what this thread is about. Many different ways to build and host a site, although many would find it simpler to just run Ghost or Wordpress and have the GUI for their posts.
You can still use a CDN in front of a very tiny VM. Some new blog engines even support running on serverless/FaaS platforms for every easier deployments, and once FaaS evolves into just running Docker containers then the circle will complete and we'll have the best of everything.
The docker-machine command creates the droplet for you, and then docker-compose runs everything for you. It's two commands and one config. It's repeatable, automated, fast, simple, and complete.
But, sure, you could do it in a more complicated way, or a more manual and time consuming way that isn't documented or automated. I think that's called the "job security" method.
It's less about "why would I use ansible?" and more about "why wouldn't I use docker?"
That heavily depends on if this is a "learn new tech" thing or not. Some people view setting up a blog as a challenge to solve, and some people just want a blog up and running so they can write. And if this does it in a simple to follow guide that is reliable, the tech behind it doesn't really matter.
