When you make payments to somebody, that disappears and moves to this phone. Of course, that saves a lot of money in printing. But in countries that are so concerned about privacy, the government will actually know  2/5  BIS - Central bankers' speeches  more about you than your wife.
They are thus left to national discretion, in terms of both design and calibration. I have just argued that the case for maintaining the main responsibility for macroprudential policy at the national level is even stronger for measures targeting the real estate market.