Is it not? If you buy an ugly ape, does the creator actually transfer copyright? If not, you literally don’t own anything more than a piece of metadata. You don’t own the url (because the person who owns the domain does). You don’t own the jpeg (because that’s a nonsense notion). You don’t own the copyright. You literally just own a bit of metadata that references a url.
It's happened though, people have made NFTs of the art of various unaffiliated artists. It might not be the most common case, but it certainly happens.