This has its advantages, especially that of not asking too much of the user's hardware. Indeed, a server can be more robust and have more data processing capacity to generate the final content - lighter - which will then be consumed by the visitor's browser.
This has created a very established dynamic today in web client-server relationships. We request a page: the back-end causes the server to process the data, convert it into static files, send it to us and we read it. Then we click on a link for another page: the server processes the data, converts them into static files, sends them to us and we read them. We do a search, the back-end processes it, the server generates it, converts it, sends it to us... and so the story repeats itself throughout the visit.
All this requires a lot of resources - from the server and the connection. The server is constantly being used (processing power) to resolve the back-end, which consumes energy and time. And the connection is constantly being activated in the many calls back and forth. In addition to consuming a lot of resources, we can actually feel the time it takes when we are browsing.
The JAM stack wants to be different. What if we made sure that all the content of a site is already ready before we ask for it and still maintain all the interactive and dynamic capabilities that exist in modern sites? As in the past, we could just call the server to send us the files without having to work on them. This requires (much) less time and resources from the server side. And less resources means less hosting costs and a much smaller carbon footprint.
Even better: frameworks like Next.js, Gatsby or Nuxt allow to render pages with information at build time (when we put the site online). Thus, static files are already populated with information.
With the use of webhooks (a call that comes from our api to inform that a change has been made), we can then regenerate the specific page that will have been edited and that, from then on, will be a static page too.
The result is a completely customizable site that still has incredible speed and requires very little server side activity.
Speed of loading, lower hosting costs, eco-friendly... The positive points are numerous!