That's how the early CMS's like Vignette worked and they evolved to solutions like WP and Drupal which are better for the web publishing use case - easier to maintain, develop, and capable of real-time UGC and publishing (real-time is crucial for SEO in commercial publishing).

Static site generators are simply a file-system caching layer. Drupal used to have one of those and it was a terrible idea as the number of page variants on a commercial site very quickly hits file-system limitations and performance is appalling. Better to use a proper CDN for a similar result but with massively reduced latency due to content being served from the edge.