There is no public ledger for cash. There is no attack surface on the devices of yourself or the other party by which your cash transaction can be compromised. There are no electronic records to exfiltrate unless one party proactively deliberately records a transaction. And if they do, there is no non-repudiation. There is no risk that any cryptanalytic advances can later expose the whole history of all cash transactions or even a chain of cash transactions. Cash transactions leave no trace unless you do them under surveillance.
I was trying to recall where I read about that. Search is terrible. Took some digging but found it here:
https://mander.xyz/post/18090719