I suppose it's because Corrupted Ore gives quite a lot of XP when smelted.
Regular smelting gives really low amounts of XP, so it really isn't viable to train Smithing purely from smelting, and it would have been very slow for Respect gain in any case.
Corrupted Ore smelting can give you faster and easier XP gains in Smithing than Smithing itself, considering how AFK it is, so the team probably decided to treat it as a Protean. Thus, Corrupted ore is great if you just want to get a lot of Smithing XP, but you're encouraged to do actual smithing as well (and not simply smelt Corrupted Ore all the time) through the Respect system.
09-Jan-2019 23:24:48