You don't seem to understand what I'm saying because obviously it's technically feasible for Nintendo to port their games. The fact that they own the hardware platform their games are run on though, fundamentally changes Nintendo's approach to designing games. And considering how successful the buissness is, clearly people like what Nintendo is making. It has nothing to do with incompetence and everything to do with the fact that they have found a niche in the gaming market, which means they can't and shouldn't try using the same business strategies as a normal game studio.
yes, i'm sure you're privy to the internal business dealings and strategy at nintendo and can speak authoratitavely as to how and why they make certain internal choices.