We have the ways to transfer only data (versus data + markup + DOM triggers) on partial requests with the even less taxing than rendering a full static page.
is it really "less taxing"? An app page that polls every few seconds to get back an empty JSON block is going to be eating up the network radio on a smartphone constantly, vs just getting back 120k HTML page, and a few CSS/image requests one time over, that may then sit there and be read (or a form filled out) for the next few minutes.
