First, let's check my layman's knowledge of metallurgy (which may not be correct). I think cast iron is 100% elemental iron. Carbon steel is maybe 97% iron, 2% carbon, and 1% other alloying metal. Stainless steel is maybe 82% iron, 2% carbon, 15% chromium, 1% other alloying metal.
So it seems like it's the chromium that's preventing the seasoning somehow since it's the biggest difference from the other two. But I'm not a scientist. Can someone tell me exactly what is going on at a molecular level to prevent seasoning from forming?