They are not photorealistic?
But also not necessarily very good icons, to me (not quite representative, at least in some cases), so I'm not sure what point you're trying to make...
Color and shape (outline, at least) differentiation making it easy to identify icons in one's peripheral vision is a really nice property for icons, and BeOS is pretty good on those fronts. The main sin of the "photoreal" icon set a couple posts up was that it leaned too heavily on two colors (black and silvery-grey), not that it was photoreal.
