The rationale for these things is that there’s no central authority, which means no one can block or undo a transaction. And so far at least, it’s true that transactions aren’t blocked. But why do you need such a system? Because you’re doing a transaction that a central authority would otherwise block, like paying off a hitman or buying drugs…If that’s what you need money for, the cryptocurrencies are the only game in town. But if you don’t need to buy drugs or hitmen, the cryptocurrencies are vastly less efficient…if you want to buy something you don’t want people to know about, you can just use a pre-paid credit card. There’s still no need for Bitcoin.