The issue here is that Nintendo doesn't care to focus heavily on the "core gamer." Third parties who make these "core" games will put them on the platforms where those types of gamers thrive. Yes, third parties are doing nearly nothing to try to grow that sort of gamer base on the Wii U, but if they have numerous other platforms they can develop successfully on, why would they? The gamers who want these games already own other platforms to have access to these games.
Ultimately it's Nintendo's "job" to grow a core base (through game releases, hardware structure, and marketing) on their console. And they don't put enough effort into doing that. So why should third parties?
It's unfortunate but true. I'm a Wii U owner and I'm not complaining. I own other platforms (namely PC) to play those games on.
