Not Nintendos target audience which are generally children and families. Third parties are usually responsible for the gruesome games or their competiton

The Wii U is dependent on third party developers and third party games to bolster the legitimacy of their launch coming into an HD War.They want the Assassins Creed fanfare, they want the COD, they want it all just like any mainstream business would.  Nintendo wants a piece of the pie Sony and Microsoft are fighting over which happen to be an installed based of over 140 million. They may have beaten them but the only thing they've proven is that they have the casuals and will not lose the nintendo faithful. Those are the early adopters. Nintendo needs those third parties.

Because kinect games and lbp are for the real gamers lol

Its naive to think that because a studio can create an awesome mario or zelda game then they can make an awesome mature game first of all... Secondly, they would really need to work on dialogue and story which is very lacking in their first party games. Zelda probablly has the most depth story wise but its no AC or the likes.

Nintendo is much more known for gameplay than it is for story & realistic graphics. I'd love to see them venture into M with Zelda Wii U, but maybe not everyone will like that.
Maybe the best course of action would be for Nintendo to acquire a developer that is focused only on M games...

Isn't ZombiU basically Metroid with zombies to begin with? For all we know, Nintendo could be making Metroid Prime 4 right at this moment.

Well Reggie went to a Wii U preorder line and pretty much stated something like that.  He asked the crowd what was turning 10 years old this day or something like that.  No one really knew and then he said Metroid Prime.  So it might be a little hint since they brought that up.

http://www.youtube.com/watch?feature=player_embedded&v=jkaYNtD55-I

at about 2:30 in video

Not true. Imagine what would happen if they took their Zelda and Metroid and made them dark as hell. With blood and guts and brains flying all over the place. Link peircing some Moblins head and the bran runs out. Or Samus shoving her gun down someones mouth and fires away.

THAT would be risky.

@OP: Yeah, I wanna see them tackle the "M-rated" market as well in some fashion.

Not true. There's a couple of million 360's out there that was bought as replacements for a RROD failure, and quite many are buying the new versions of PS3 as well. And I know A LOT of gamers that has both the 360 AND PS3. The install base is not 140 million. I'd say, by a hunch, that the install base is somewhere between 100-120 million. Still a pretty damn sweet pie though ^^

I think early signs point to Nintendo being proactive in the Mature rated games. i.e. helping out with Bayonetta 2 financially and helping with dev and publish the cleaned up version of NG3.

let's hope they continue on this path and not drop it.