Mainstream economists do not understand the problems with maturity and risk mismatch, also named liquidity mismatch:
The IGM forum responses to this statement “There is a social value to having institutions that issue liquid liabilities that are backed by illiquid assets” are depressing.
The problem is that illiquid assets do not actually properly “back” the liquid liabilities, or they back them badly and unsafely.
The quality of the liabilities depends on the quality of the assets: illiquid assets imply illiquid liabilities. People may wrongly believe they are liquid, but in fact they are not, as banking and financial crises show.
It is like selling security services, making people think they are safe, and then providing the service poorly, so that risk is actually much higher than people think it is.