Locally I've seen some businesses refuse to accept cash, although they should, according to law. They only accept cards, ...
(emphasis mine)Are you sure? In many countries it seems a particular fiat currency cannot be refused as a means of
satisfying a debt. When you wish to purchase something, you are not in debt to the vendor and are typically free to negotiate the medium of exchange, with both having the legal right to refuse to trade.
Furthermore, I suspect that even in satisfying a debt, you might still lack the legal right to force your creditor to accept fiat cash. If some form of currency is "legal tender" for debts that doesn't necessarily mean that an official physical form of that currency must be accepted. I would expect the law to contain loopholes to allow creditors to refuse, for example, sacks of coins.