Many in here have articulated on why......why put in the effort for very little payoff when many will buy the superior version anyway, with things such as a better, unified online infrastructure, a larger multiplayer install base, etc? There's simply no reason when you view it from a business perspective.
I don't agree with Nintendo defenders that they don't need 3rd parties, and I don't buy that those who buy Nintendo systems only buy them for Nintendo games even if 3rd party games existed, either. Sure, that's true now because that's all you can buy on their wares, and what other games are available lack in numerous areas due to Nintendo's lackluster efforts. But if they brought to market a system that held hardware parity in the same realm as Sony and MS's offerings (which would make ports easier, cost-effective, and competitive), kicked their online platform into 2014, and took the effort to really attempt to court and work with 3rd parties to bring software parity as well, Nintendo after a period would then have a one-up on the competition in addition: their 1st party.
They need third parties because 1) it establishes a solid user-base that can then grow such things as their online and digital markets into, 2) it fills in the droughts and sustains momentum. Would 3rd party games sell like shit at first if all this happened now? Yes, because through Nintendo's neglect and chronic ineptness throughout the years they've allowed parts of their business to atrophy and reside in relative mediocrity, not least to mention given their philosophies towards them it would take some time to repair bridges. People will always choose the better option, and Nintendo just doesn't offer that. When people say, "well, why should 3rd parties bother? No one will buy them anyway....." they speak as if Nintendo is somehow the victim. No, it's Nintendo's doing, 100%. They give no incentive over alternatives that are much better executed by companies that don't insist on running their business with mentalities stuck years prior. The trouble they have with 3rd parties today extend FAR back into the past, not only through actions, but philosophies (such as Yamauchi famously referring to them as "garbage companies" and Iwata claiming "no one want online games").
Is it no wonder, then, why 3rd parties aren't too keen on putting their games on their systems?
But in Nintendo's continual arrogance, they like to believe they somehow exist in a vacuum and don't compete and that people will always buy their product no matter what. They are exceptionally delusional, and they are now paying the price for it. They need to realize that even though they think they aren't competing, that doesn't matter because consumers see it very differently when it comes to where their money is going. You'd think this would be a self-evident reality in any business, but in their incompetence I'm sure they're so obtuse they don't have a clue as to what's wrong.