Because if your application bundle is a fixed asset — like a JS SPA that fetches it’s data from an API then you can distribute your entire application via an inexpensive CDN.
As soon as your application bundle is rendered on your servers dynamically then only part of your site can be delivered via CDN.
Basically going all-JS gives you an app model where your sever side code doesn’t even know or care about HTML or the web or whatever. It just pushes JSON or whatever around and it largely client independent.
Great model when you need to support iOS, Android, web, desktop.
As soon as your application bundle is rendered on your servers dynamically then only part of your site can be delivered via CDN.
Basically going all-JS gives you an app model where your sever side code doesn’t even know or care about HTML or the web or whatever. It just pushes JSON or whatever around and it largely client independent.
Great model when you need to support iOS, Android, web, desktop.