A bank cannot accept crypto because the system that was used to build cryptocurrency is opposite of the core of the banking system. One of the points of crypto is to provide decentralized system opposite to the centralised banking system. To prevent major crashes and the huge impact by decentralising it. Banks see the blockchain as their competition and potential acceptance and involvement of the cryptocurrencies by the governments may be threatening to the banks. I believe that all smart and progressive nations will make a balance between these two. Letting crypto currencies have their role, but keeping to the core of the standard and centralised banking system. Maybe banks will adjust as well and involve cryptos in their business.