Because the line one draws is "no server-side code at all". If you use a bit of code for that, you might as well use a bit for this, and for the other thing, and soon it's a CMS.

Besides, the hosts I want to deploy on don't have PHP (S3, stock nginx, Github pages).

Fair enough.

I switched our team's website to a completely static site a few years ago, they were using joomla (vomit) for essentially a broucher site that changed once a quarter.

I wonder if there would be a place for a 'json search as a service' thing - where you could upload your static content (as markdown, rst, txt, whatever) and then use their servers for full text queries which return a json list of matching page URLs and titles...

Because "no server-side code" means "I can host it completely on a CDN", which pretty much solves the scalability needs. If you need to scale those few lines of php or whatever language, this is gonna be much more difficult.

Plus, you can host it on different platforms such as freenet, gnunet, and have the simplest backup ever (`cp` is enough for having a functioning version on any OS of any kind).

CGI is pretty much never better.