NFTs were created for the very reason that certificates of authenticity have no value unless the ledger from which they were issued is not public.
How can you know there wasn't more certificates printed than tee shirt created ?
How do you know it's a real certificate in the first place ?
How about you loose the certificate ?
Seriously there really is no reason to not prefer a digital certificate versus a physical one, it is on all accounts superior.
You certainly wouldn't argue cryptographic keys are useless because we have physical ones on any other matter if it wasn't for following the "I don't like blockchain" trainwagon.