"Electronically displayed type attempts to imitate printed type—it has no choice in this matter. But while our entire typographic tradition (and calligraphic tradition before that) is based on black letters on a white background, electronic devices always display black by also using gray or color. It's a technique called font smoothing. Crisply defined black characters do not exist in this electronic world. All text is intentionally made slightly blurry (see**Figure 2**) to smooth out what would otherwise be jagged-edged characters, where individual pixels are distractingly visible."
"Electronically displayed type is normally rendered using shades of gray (top, in 14-point) to make its component pixels less visible. The type looks less jagged, but it's also blurry. "
http://www.adobepress.com/articles/article.asp?p=1747367&seqNum=2
It seems that "something" in particular decide people to prefer blurred edges to jagged edges or the opposite as the author of this text says that individual black pixels are distracting whereas I find myself that, on the contrary, shades of gray or colors added to characters are more distracting.
In an ideal user interface, everybody should be able to choose what they prefer though, in my opinion, without the creator of this interface, Microsoft here, choosing themself what they prefer.
I guess it might be kind of resolved when higher PPI screens are available on all devices though. I don't have the same problem with anti-aliasing on screens having around 200 PPI (my computer screen has around 100 PPI).