Because for a lot of use cases, there's simply no need to have a full LAMP (or one of the many various alternatives) stack to serve what should be a simple webs

Because for a lot of use cases, there's simply no need to have a full LAMP (or one of the many various alternatives) stack to serve what should be a simple website. I'm not sure quite what you think static site generators do if you're comparing them to a CDN, but they take a set of scripts, markup, images, and whatever else you care to mix in, and then emit a static site - just a bunch of HTML/CSS/JS/etc. You can host it on anything that supports serving static files - Google Cloud Storage works (especially when fronted by Cloudflare, data bandwidth between those two companies is cheaper), a random old server, etc. You typically render it locally, then simply upload the changes to whatever you're using to host. Not all websites (and not even all websites dealing with somewhat dynamic content such as blogs) need a full server stack, and the security of the server is far better if it's just serving files. I transitioned my blog from Blogger (when they updated it last summer and absolutely ruined the core functionality of their editor, which is editing text) to a Jekyll-rendered site. It works out well, and I simply integrate a Discourse instance I run for a variety of things into the templates to have a functional comment section for posts.