Seems very unlikely that the absence of ClearType sub-pixel anti-aliasing is a bug - it's missing from the Metro/Modern/Immersive environment in Windows 8 and also random elements of the desktop UI (the clock, the language switcher, Windows Explorer window titles, titles in taskbar window previews and likely elsewhere), not to mention IE10 and Office 2013.

We can only speculate as to why it's fallen out of favour - possibly due to its incompatibility with tablets that need to support multiple screen orientations.