I think it is more like nobody knows and cares cause they can use dual monitor in x window environment.
It make more sense that way. However, I can see the need of scrolling a big file, so you can have two or more monitor stack vertically.
I have a dual head card which displays exact same thing in both monitor in run level 3.
I used to want to make my video card to run at 85 Hz in runlevel 3, nobody replied to that either.