JSON at least I pretty much never see being generated from templates. In the few cases where someone I worked with suggested it I've easily argued them away from it. The difference between JSON and HTML in this regard is illustrative. Every language already has a data structure that is easy to manipulate and also to translate directly into JSON. There is generally no built-in "DOM" data structure. And even if you have one (as you do in browser JS) or find a third-party DOM library, it's usually awkward to manipulate.