1) The ports were mostly bad or late or more expensive
2) Gamers with more than 1 console/PC tend to buy the thirs party games there, because reasons (Bigger multiplayer userbase, better friend management, better online, etc)
I do prefer games on Wii U because of gamePad functions (even a map or inventoru management) and Off Screen Play. I got Lego City Undercover, AC4, ZombieU, Child of Light, Trine 2, Nano Assault, among others.
The only let down was AC4 not having the DLC there. But if the game is not too online oriented, i prefer them on Wii U.