@lxo modern webmasters don't "shift" the computing costs, they use client-side processing and caching to avoid transferring redundant data which the user may not really need and that would only hog the service back-end. Here, JavaScript is used to guarantee a fast and smooth service for everyone. 😉
Websites change frequently, so amateur automations can be dangerous and unreliable. If the webmaster wants to allow automation, then the website will offer public APIs.
CC: @tennoseremel @quasi