I have recently acquired weak glasses (0.25). I wear them when I'm watching good HD sources and take them off if there were significant artefacts or low res source as they are better slightly blurred and there is the comfort benefit.
I do care about video quality although I know that I'm in the minority (many people say that picture quality is the most important thing in a TV but very few of them can actually identify it). Given that my very weak prescription makes such a difference (720P and 1080P content is probably the same without my glasses) it wouldn't surprise me if many people really couldn't see it.
