The tl;dr on why IO is important is you can just use (effectively) one program, but stuff different secrets inside them with a guarantee that no one can pull those secrets back out.

Cryptographers have proven that it's possible to use this as a primitive from which you can rebuild the rest of common cryptographic primitives (public encryption, symmetric encryption, etc). So--if it's possible to put this together it'll be a novel construction for every cryptographic primitive that also dodges some of the problems with key distribution and negotiation.