Fiat game mechanics force them to "invest" in "productive" assets in order to stay ahead of inflation.
Scare quotes used because a ton of the price of those assets now reflects a monetary premium. I.e. a portion of the price of a house is its value for living or renting out in a given area, but a lot of it is its value as a scarce asset that is somewhat resistant to inflation.
Needless to say, this is not a great allocation of resources and is an incredibly inefficient way for saving to work.