Why aren’t all NS1 games compatible with NS2?

This might be an ignorant question to ask, but why isn’t the Switch 2 fully backwards compatible? The WiiU had a Wii environment.
Why is this not possible with the Switch 2?

I understand it’s different hardware and software, but why isn’t there a way to load the original NS1 environment to boot the older games?

If they improve upon the backwards compatibility, is there a possibility that all games from the switch 1 will work in the future? What can be done?