Nintendo doesn't "always" miss the mark. You have no idea what you're talking about. Nintendo has dominated handheld console sales since the 80's. They have 3 consoles that were the top sellers in their respective generation; NES, SNES, and the Wii. They are a multi-billion dollar company.
Nintendo's DNA is very similar to Apple's, in that they like to drive the entire experience. If Apple followed your suggestion, they would port the iOS over to Samsung phones to make a quick buck.
Bad idea.
Even a multi-billion dollar company can only bleed money for so long, what with the Wii's more lackluster sales later on followed by the Wii U not-so-hot sales numbers. Here's hoping they can find renewed success in the console market with the NX.