Have you even had Control-C take forever to kill that `cat` you accidentally ran against a 1GB log file? I have. Most terminal emulators are 'dumb' and try to render the whole backbuffer sequentially even if what you are seeing is no longer the tail of the output stream.

It's not so much that this is 'fast' (because even gnome-terminal which is not what I'd call crazy fast is 'fast enough' most days), but that it's much more responsive as a result. By locking the terminal refresh to your screen refresh rate and only rendering 'current' data this removes a lot of headaches you can run into with other terminal emulators (like the aforementioned cat of a 1GB text file).