Unfortunately, they need a good cleaning real often to prevent this. I clean mine on my cars about twice a week average-extra work, but so far wife's mercedes has 41K on it, and wheels still look almost new. Our smart wheels are still too new, but I would think the same treatment would help hold the "pittedness" at bay....
Maybe one of those brake dust shields that I see advertised here and there would help. Anyone have/try one of those?
Brian