Well that's why. No one cares about the Wii obviously. I guess Square Enix thinks that since people were dumb enough to buy a system with no games, then people might purchase a bunch of DLC for the specific system.
I'm kidding, there are people who care about the Wii. Even if it has no games.
I wouldn't think DLC on a game like My Life As King makes much of an argument. The game itself is DLC as it's a Wiiware title and doesn't come on disc. The game also sucks regardless, so yeah.