What's wrong with Chicago? Chicago was genius. Old Macs had black and white screens, no grayscale. But grayed-out text was a necessity for showing disabled or unavailable items in the desktop GUI Apple was developing. Most bitmapped fonts are completely unreadable if they are checkerboard-dithered to appear at 50% gray on a black-and-white screen, because they have mostly one-pixel lines in their glyphs. However, the 2px-wide vertical lines of 12pt Chicago allow it to be completely readable when dithered to 50%.

It was a font built for specific requirements; on today's million-color screens it's out of place, but at the time it was introduced, it made perfect sense.