Usually, when a publisher takes in a game from a developer, the developer sells the rights to the idea. Meaning the publisher takes full ownership of all trademarks to the game and the contents that go with them, while the developers own nothing. Nintendo does things a bit differently. If you look at the copyright info for all of their non-in-house properties, you'll notice that most of them are jointly owned by their respective developers, in conjunction with Nintendo. Nintendo's really the only major publisher who let's most of their studios keep partial ownership of the IP. Why is that? 

Is it because Nintendo trusts developers more, or has some philosophy regarding letting developers keep some of their work?