It is enforceable, it’s just that not all countries are there yet. It’s practically impossible to buy anything worth more than 1000 eur with cash in Scandinavia, ironically with the exception of drugs. Humanity is on a steady track to a world where authorities are controlling every penny, at which point non-sanctioned opposition is impossible.

You can only enforce limits on cash transactions, if at least one of the two parties involved in the transaction is interested in enforcing the limit.

Which is trivial to ensure when people effectively can’t deposit cash to their bank accounts and businesses don’t accept cash - nobody wants the headache. Which is exactly what happened here.