Why do things vanish into thin air but never into thick air?
Why do some things happen in broad daylight but not in narrow daylight or broad nighttime?
Why do remarks sometimes offer cold comfort, but no remarks offer warm comfort?
Why do we speak of salad days but not salad nights?
Why do we speak of the mind’s eye but not the mind’s ear, the mind’s nose, or the mind’s tongue? (We can surely imagine a sound, odor, or taste, as easily as we can imagine a picture.)
Why do we sometimes go whole hog but never go half hog (or partial hog)? Similarly, why do we sometimes go full-bore but never half-bore?