After so many years it's still shocking how willfully people buy into third party excuses. Third party support isn't about horsepower, ease of programming or even sales. It's first and foremost driven by bias.
There are people here who seriously argue that the GC's storage medium was a notable culprit for lack of third party support, but don't you guys realize how difficult the PS3 was to program for? But not only had Sony created a monster, it also led to a year where virtually every major third party player posted a loss (the only exception I remember is Disney Interactive). That's a significant difference to the Nintendo situation where games simply didn't sell as well as third parties hoped for; so you are looking at too low profits for third parties on one side (Nintendo), and outright losses for third parties on the other side (Sony). The PS3 was also in third place. Yet all of those factors combined didn't lead to third parties dropping support for the PS3, instead it became the lead platform for development in many cases. Third parties were willing to endure losses to keep PlayStation in the game.
Not too long ago there have also been interesting quotes from Square-Enix and Nippon Ichi concerning the Japanese market for dedicated gaming devices. Both companies stated that they have to drive the installed base of PlayStation which runs contrary to the premise that third parties don't consider themselves responsible for moving hardware because that's the console manufacturer's job. The obvious question is why don't they develop more games for the 3DS which already has a huge installed base and sells the most third party software in Japan. And that's when you should realize that not even sales play that big of a role in determining third party support. It's first and foremost something that is driven by bias.
I agree somewhat with this, it's a view I have as well only the thing behind the bias is developers wanting to be in control of the industry rather then the platform holders. Sony and MS utilize approaches that give developers and publishers more control over the industry so they'd rather see those platforms succeed, Nintendo's approach puts the platform holders more in control and that's what it comes down to.
What people don't understand is that if developers began supporting Nintendo as equally and they became market leader consistently both MS and Sony would gladly adopt the same approach as Nintendo and the industry would mainly be back in control of platform holders, this would mean it would be harder to pull things like the Evolve DLC fiasco or release games that are bugged to hell until a patch comes out (Skyrim PS3 anyone). Developers don't want that as they won't get away with a number of things they do today and can't be lazy either so will use any excuse knowing that people will believe it at face value no matter how silly it it, some people still believe the Wii U is only as powerful as the 360 for reference.