Big pages usually have repeating sections in them, like rows in a table. Only one copy of each repeating section need be present in a jswapl template, it loops the section as many times as needed by the dynamic data.
Conventional web app frameworks like PHP do all this work on the server and deliver complete pages to the browser, even if only 5% of the page is dynamic. jswapl can reduce bandwidth usage by 90%, speeding up content delivery and reducing server workload. It's like cloud computing, the browsers provide the processor power and their users don't mind because they get to see the content quicker.