> I'm not sure even operating systems do

Oddly enough Windows used to be a lot better at what you describe than it is (in practice) today. I've used old systems where it took 0.5sec to clear the screen, and you could see the color sweep down the monitor from top to bottom. Now THAT is slow. Because of that the OS used a lot of tricks to minimize drawing, such as xoring the caret, and precisely tracking dirty regions to minimize the number of pixels drawn, etc.

Much of that finesse has been lost in this new generation of GUIs built on 3D APIs where the entire window is thrown away and redrawn every frame.