For example, I work on a large, enterprise webapp, it has the frontend UI, which users interact with heavily: this, we have built out using clientside Javascript which interacts with the Rails backend via an API.
However, we also have an admin area -- many of those pages are used very rarely and are quite complicated. I initiated a change to build these panels using traditional server-side rendered ERB views. In the context of our codebase, it takes less code and it's easier to iterate on these without bothering with the Javascript framework.
In other cases, like my personal blog, I use Jekyll to generate a bunch of static HTML and, essentially cache all this on Github pages.
Javascript frameworks are amazing and can provide a much richer, much better experience. But, I don't necessarily think they're appropriate for all problems. One other big reason why, it just the inherent "experimental-ness" and, the churn / quick obsolescence you may find in this area. Some problems don't need to be re-solved every year or two. :)