The art being recorded on a blockchain or not doesn’t matter - what you’re selling in an NFT is a signature not the art. An NFT is a decoupling of the art and the signature, because digital art is infinitely reproducible. The NFT introduces scarcity - but only for an authentic signature (which can’t be faked) not the digital art itself.
And want you’re saying is not necessarily true - my understanding is that some markets do place the art on IPFS, but I’d have to look into it’s exact working to know for sure.
But I believe for the old Hic et Nunc that was the case.
In this particular case - it is better than a standard contract because the previous method of authenticating work is hugely expensive for the artist and has immense gatekeeping. Minting an NFT takes 30 seconds. Getting you work into an art gallery takes months if not years of battling and requires other people to make the decision whether they want your art in their sales space or not. In crypto you can just do it yourself and figure out your own personal authentication method (usually twitter).