Could you elaborate as to how? Examples aren't synonymous with rasterized images. They use font-face in the example column where they display Open Sans.
It's not a big deal but I just didn't understand your response
It's mainly because the raster images are going to be more accurate than @font-face as they'll display properly amongst all browsers and OSes just like a PDF would.
edit: Also the most obvious reason (which I forgot to mention) is that they are type specimens and type specimens are (AFAIK) always done in raster images.
It's not a big deal but I just didn't understand your response