I just ask people to consider that even though we all have bank accounts and we take that for granted, there _are_ actually people who don't, and they're not operating a criminal enterprise.
My grandparents came as refugees. My grandfather has never had a bank account. He bought a car with $50 bills once. It was so funny, they were all stuck together and the clerk had to sit their and peel them all apart one by one.
He needs expensive surgery soon which isn't covered by medicare. He's going to pay for that with cash, too.
If a ban prevented him from paying for that surgery with cash, he just wouldn't get the surgery. Or, he'd give my mum wads of cash and make her pay for it (and then she'd have to explain that to the tax office, and he'd have no privacy).
In his home country, you couldn't trust the banks, so people hid their money. Of course that kind of thinking is silly in Australia, but good luck explaining that to someone with war-trauma.
A lot of these old Europeans are like that.
[1] https://www.abc.net.au/news/2020-12-07/cash-ban-law-10000-do...