I also use to kinda wonder about the connection between the onchain data, and the offchain reality, especially when people talk about using blockchains for supply chains. What mechanism do you have in place to get them to sync?
But when it came to NFTs and art, I think it lines up. It use to be the enjoyment of a piece was inextricably tied with the ownership of something. It was the way physics worked.
And then, we had photography and subsequently digital tech, and now we are able to separate the ownership of a piece from the enjoyment of a piece through a digital copy. Now you can enjoy a piece without ownership!
But aghast! What does that mean for value of ownership? Well, the social contract we all collectively came up with is that the original physical piece is worth a lot, and a copy isn't, regardless of the technique. And we have lots of mechanisms in society to enforce that, from people that specialize in detecting fakes to the court of law.
It also kinda worked, because while you could digitize the painting, you couldn't digitize the ownership of an art piece--because there was only still one original. So the ownership (not the enjoyment) of a art was still scarce due to physics and not digital, because for the longest time, we didn't know how to make digital things scarce and original. In fact, we thought that's why digital was so great. No cost duplication has changed the world.
But, apparently, you can make digital things scarce. Through cryptography.
So if you view this as a progression of the separation of ownership and enjoyment, the enjoyment got digitized first. And now, we're seeing ownership being digitized. But ownership is kinda weird because it's both digital and scarce!
Back to the connection, I think the connection is simply a social contract in the way money is a social contract. "This NFT represent an ownership for this art piece."
I think there are ways around it, for future works. I can imagine art pieces being procedurally generated by a computer, but hand picked by the artist. The artist then records the parameters for the procedural generation inside of the NFT. Then, any owner for the NFT will be able to generate the art, and that would be the connection.
At the end of the day, that still relies on some social contracts, like agreement that these parameters is applied by this procedural generation algorithm, etc.