[9dev]

Because you're thinking in the context of a solo developer working on their site locally. You don't need a CMS. People that want to collaboratively work on a website, some of which may lack technical skills, need a way of previewing their edits that doesn't involve running shell commands.

[Lammy]

You're conflating the two unnecessarily. There's no reason Jekyll's server has to run on the editor's local machine. See my other comment about jekyll-admin which can be used collaboratively: https://news.ycombinator.com/item?id=47737324

I don't see much of a difference between `jekyll serve` and the e.g. `service nginx start && service php-fpm start && service mariadb start` that would be needed to run WordPress. In fact I don't run my WIP Jekyll site on the same machine that I edit from. Mine is available only on my personal mesh VPN, but it could easily be available publicly if I wanted it to be.