"Bitcoin transaction is irreversible". I would have loved it to be, but there are reasons why it's not. Also, a transaction that was made from one bank account to another is irreversible too. So it's not new.
I don't know the details but if for some reason you make a wrong wire transfer the bank should be able to get the money back. And if you receive some money that you were not supposed to receive and you decide to simply keep it/spend it then you are going to be in some serious troubles. With bitcoin none of this happens and I never know whether consider it something good or bad.