It's not just about Nintendo being "nice" to developers. The issues Nintendo has had with third parties is a history that is long and deep. And unlike Sony with the playstation and what looks like the ps4 and Microsoft with the 360, Nintendo has never fully embraced catering their hardware and infastructure to accommodate and please third parties.
Even today you see the complaints of developers, stories of nintendos poor communication with certain companies, poor infastructure, still behind in areas that many developers consider key to their revenue streams like online, odd hardware decisions that, for instance, ignore the current trend of similar PC-style architecture that allows easy ports and easier development across platforms. I could keep going but hopefully you get the idea.
I said in another thread but Nintendo should of been out Sony'ing Sony this gen if what they were really going for was the core gamer and bringing back third parties. They have more work in the confidence-building department with third parties then either Microsoft or Sony. They should of been working with third parties day one of the the consoles design and made sure all the bullet points developers typically ask for are hit and hit hard. If not then they honestly should of stuck to a more wii-centric formula and created a low entry cost box that catered to Nintendo fans, casuals, and low cost games that could help yield developers a quick profit and perhaps grow a few high quality niches(for example: lower cost, high quality RPG's, indie games, ps1 style niche games that need less revenue to be profitable but help diversify your audience, maybe strike a deal with google for android as your operating system and bring over much of their applicable games library day one etc). Instead Nintendo has chosen what seems the worst aspects of both business paths.