> it's a static site and not using something like Rails
There's nothing "static" about this site. You're still querying a back-end database, you've just outsourced it to a third party. And looking at the example site, it doesn't exactly seem "simple" to me. Hell, instead of just using one (heroku) this one relies on TWO (netlify and the authors, takeshape).
This "stack" seems to be mainly being pushed by the people trying to sell the 3rd party backends.