During most of human history, before there were banks, "saving" usually meant saving some form of grain from one year to another. More likely, more than that would be lost to rot, virmin or brigands.
Gold did perhaps not decay the same way, but if the harvest was bad one year, the price of grain could go up radically, so saving grain directly was safer. Also, grain was harder to steal.
As society became more complicated, one could pay a goldsmith to store the gold in a vault, though there was still a risk that the gold would be lost to fraud or robbery, eventhough the vault was still probably safer than to store gold in private homes (if you did not live in a castle).
Up until this point, the time preference of money would tend to be negative whenever people were saving. Better to eat normal today and be sure to have enough next year, than to eat double today and maybe starve next year.
Some goldsmiths would lend this gold to lenders, at an interest, and the honest ones would pay the depositors an interest in turn, to compensate for the increased risk. Still, it did happen that banks went bankrupt, and deposits would be lost.
Only in the last handful of generations have governments guaranteed the bank deposits, and only for a limited amount.
Meanwhile we had the industrial revolution, and the population and economy was booming more or less for 200-250 years. This, combined with the growing banking system, caused a positive time preference for money, and people started to expect that saving was not only safe, but should also produce profit, not just safety.
Lately, however, both the economy and population have stopped growing, more or less, and the time preference of money is roughly back to neutral, if not slightly negative.
In such an economy, it simply doesn't make sense to have a currency that allows people, without risk, to "teleport" wealth from now into the future. We already tried that in 1929, with deflation causing mass economic destruction. A lot of savings were still lost when banks went bankrupt.
With a moderate interest rate (ideally around 2%), the economy can handle a somewhat negative time preference for money as much the population gets older and less in need of instant consumption. When the interest rate for deposits is lower than cash savings, the difference can be seen as the insurance premium for relatively risk free storage of value. Those who want a profit (or at least lose less), have to accept some more risk, and invest in other, riskier asset classes in such times.
As long as the interest rate is low, the currency still functions as intended as a medium of exchange and measure of value, while still being tolerable as a short term store of value.
Clearly, though, as the inflation goes to 10% and beyond, all features of the currency are hurt.
But next time you're annoyed that your deposit falls in value about 2% in a year, just imagine how it would be if you were saving grain in a silo, and found that the rats had been eating half of it.