Banks are subject to banking laws and various oversight authority/agency policies.
Around here the banking authority started development on new ACH features (4 hour transfer, and they are developing "instant" transfer, and hopefully 24/7 transfer too), and the banks have to get on board in 1-2 years. (There's a deadline. Sometimes it gets extended because too many banks fuck up, but they get fined. It works up, progress happens.)
So, it's very, very, very far from impossible. If there's political will, it can happen in about 1-2 years.
Around here the banking authority started development on new ACH features (4 hour transfer, and they are developing "instant" transfer, and hopefully 24/7 transfer too), and the banks have to get on board in 1-2 years. (There's a deadline. Sometimes it gets extended because too many banks fuck up, but they get fined. It works up, progress happens.)
So, it's very, very, very far from impossible. If there's political will, it can happen in about 1-2 years.