Who cares about corner sharpness?

When I look at lens comparisons (e.g. at the-digital-picture.com ), I notice that lenses are often compared on the basis of (among other things) corner sharpness.

I can understand how center (and near-center) sharpness is a big deal, but do you really want your corners to be super-sharp? Heck, it might be nice to have them a little blurry in order to draw attention to the main subject.

What am I missing here? Have lenses gotten so good that we need to find some nit-picky thing on which to compare them?