alt Hacker Newsone of the big problems of the great depression was banks went bankrupt left right and centre, and took everyone's life savings with them. Also as a lot of banks generally hold mortgages in their portfolio, so when a bank collapses it means that mortgages all get fucky too.
So the mass printing of money meant that banks didn't collapse.
It also meant that a fucktonne of cash went into the hands of the uber rich.
This is one of the reasons safety nets on savings exist in both the USA and in Europe (and probably other places as well about which I'm less informed). Even so, the tacit understanding is that this is more about preventing bank runs than about the practical effects on the currencies involved because it could very well be that that insurance will pay out in money that is worthless.