Have you ever tried using a small device with a full HD screen? We recently got some 15" laptops at work with full HD screens and you have to turn the text size up to be able to use them. At standard everything is far to small to use comfortably.
If you had a full HD screen in a 10" device with this tablet OS then things would just be scaled to the same size as on a 720p screen. Its another one of those features that people seem to think they want, but in reality don't.
I use Windows 8 on my rMBP at 2880 x 1800 with no problems (It's also my main OS).

