Why are some Nintendo fans so opposed to going third party?

[Purple]

phenom08 said:
Why no mention of 3DS at all? Purple this only makes you look like a Ninty troll, you do realize this right? Whether you like it or not, there handhelds lead the market and that's without Nintys full support. Hell a smartphone is more likely than 3rd party.

I'm not here screaming at them to go third party. I'm just asking why some people are so opposed to Nintendo going third party when there would be so many benefits. Someone mentioned the controllers and I agreed.

I didn't mention the 3DS because there's no need for Nintendo to go third party in the handheld market. I think the 3DS better suits the markets needs for portable gaming than the Vita does.