>> if you can't delete the jpeg, alter the jpeg, move the jpeg, hide the location of the jpeg from public scrutiny, or stop other people from downloading, copyi

>> if you can't delete the jpeg, alter the jpeg, move the jpeg, hide the location of the jpeg from public scrutiny, or stop other people from downloading, copying, modifying, and redistributing the jpeg, in what sense do you own it? You are not paying for the jpeg, you are paying for the (digital) signature of jpeg's author, or some other famous person. For example, a picture of sunflowers bearing my signature is worth zero, but if it were signed by someone with the name van gogh, it's worth millions. However, the signature of the latter can be forged, and has been forged many times successfully. It's very expensive to verify authenticity of a physical signature. That's the problem the digital signature on a blockchain solves. The NFT site verifies the famous person's identity, and appends an unforgeable timestamp. There are a finite number of famous people, so the resulting digitally signed item is scarce. That's where it's monetary value comes from.