Not agree with you on this point. Otherwise, let me ask you. When buying something and you pay with coins/banknotes, how are you protected? You can't go to the police and the bank and say my banknote has the number #xxxxx printed on it. As of today, it hasn't been a problem to spread this method of payment. Same thing when gold was used to trade
When you pay in cash you usually get a receipt.
Usually aka 100% times in a civilized country and not in a 3rd world slump.
That is your proof you have paid and this is how things work fine for ages in Europe.
If the cashier is handing you the wrong change and denies taking your money you can of course call the police and have the cash in the machine searched and counted. We have a law in place here that while working as a cashier you are not supposed to have more than the equivalent of 5 euros on you.
And do you see this "civilized" arrangement easily replicated with anonymous and "illegal" cryptos ?