Because when I buy a piece of art, I can hang it on my wall and look at it.

If I buy an NFT, it doesn't give me the right to print a picture of the art and hang it on the wall. I have no rights to display the picture of which I own the NFT. All I can say is that I own the NFT of that piece of art.

So, I can hang the hex code of the NFT on my wall and look at that I suppose. But the actual piece of artwork that is associated with that NFT? I can't even display it on a digital display in my house, because that's copyright violation.