Earlier quoted context omitted.
You said cash is neither convenient nor safe. I've paid with cash, and I find it convenient and safe. It's especially convenient when the seller only accepts cash, since a non-cash transaction would be impossible. I have no problem with France's law against cash (since I'm not a French resident). France also doesn't have freedom of the press, and I'm ok with that.
You said cash is neither convenient nor safe. I've paid with cash, and I find it convenient and safe. If it's generally known that nobody carries large amounts of cash, I imagine it might make muggings a bit less common. It's not so much you personally carrying lots of cash that's safe or unsafe, it's what fraction of the population carries lots of cash that makes things safe or unsafe.
Muggers are after enough money to buy drugs, and so they don't care if it's a few dollars.