Have you ever tried to do interactive scrolling on a window with throttled updates? I have (while debugging Emacs scrolling). It is intolerable, very like driving with a variable lag in the steering.
Scrolling text efficiently is not best solved as a problem in general video compression: we know a lot about the nature of a scrolling window and can come up with very much better examples. (Proof by example: core text X scrolling back in the day, or X scrolling with XRender objects now that glyph cache defragmentation is implemented. It moves so fast that all you can see is a blur. I would consider it a very serious regression if it only updated a few times a second! Perhaps this doesn't matter much for xterms but it certainly matters for text editors. And I spend my whole day in one of those.)