Purely a guess, but I'd say the alcohol rinses away the standing water on the blades, leaving only the airborne moisture to deal with.

Back when I shaved with a razor, I'd store it in a cup with baby oil. Did work to keep it sharp longer.

This works wonders for preservation (both sharpness and rust). You can also sharpen them by running it backwards on an old strip of denim a few times before each shave.