This is why we need to preserve old games, and why Nintendo should have a game preservation team just like PlayStation!!
You're mixing up preservation with distribution. Nintendo preserves their games. That's how they were able to release an almost 30 year old incomplete game by the name of starfox 2.
Nintendo is probably one of the best at preserving their old code, actually. They just don't distribute that code to the masses. In fact, rumor has it, they have the source code and/or a final ROM for every game that has ever released on any of their consoles.