Screen rotation is also a thing on desktop. My Dell has three external monitors, side by side, all rotated in portrait; use a decent window manager and you can have a decent 3×2 grid of windows that easily leads to Perfect Window Placement™ just by using Move Window to Top (Bottom) Half. Gnome and pals know how to handle both horizontal and vertical RGB subpixel arrangements and automatically switches configuration as you rotate the screen.

Mobiles and tablets have such high resolution monitors nowadays they probably run without subpixel AA at all…