Cabbage can indeed, examined carefully, be extraordinarily aesthetically pleasing. Even the most ordinary culinary cabbage has an interesting structure to it, a satisfying mix of geometric regularity and organic variation. The structures of a Savoy or other more elaborate variety deserve closer study, so much so that I'm not sure why anyone would grow a purely ornamental cabbage. There must be something in it, though. Judging by the number I've seen in recent weeks, there may even be something of a fad for them this autumn.
My local pretentious florist's has them alongside the overpriced roses, as if an ornamental cabbage were something one could present to one's girlfriend and be understood as romantic. Perhaps it is; I've never tried.