It can. Zero interest rates are the natural rate for money - since it is costless to produce. Therefore that is the optimal rate for the currency issuer. There

It can. Zero interest rates are the natural rate for money - since it is costless to produce. Therefore that is the optimal rate for the currency issuer. There is no need to pay people not to spend when you can tax them if they do. That's just basic income for rich people. Banks then discount assets into liquidity at a markup over zero and they can be allowed to compete fully and go bust which controls the net interest margin. If you optimise the system so it operates on maximum liquidity then you lower the cost of business investment while selecting for productivity by moving the business to where the people are rather than the other way around. That gets you around the greying population problem without destroying your society - by learning to do more with less. Japan has gone some way down this road, but not entirely.