Using banks means that we run the risk of the money not being printed

The deposit guarantee enables banks to print money out of thin air because it means that bank deposits are no worse than (other forms of) cash, as a store of wealth.

Because fiat cash is entirely symbolic (of what?) and has no intrinsic physical worth, it is possible for other nebulous forms of money to affect, influence their price.

Because of deposit insurance, it is possible for the market to value a promise of the issuance of a unit of currency equivalently to the actual currency itself. If people doubted the reliability of deposit insurance, they might take their money out of the banks and create a discrepancy (in price) between the two forms of money. But people value the promises equivalently to the actual cash, perhaps even because they are not aware of there being an implicit promise only, and not actual cash. They might think deposits are real money, but they are not they are merely a promise of cash from the Government.

To rely on banks and to trust that deposits are safe there means that we are trusting the Government to provide and print the required banknotes in the event of a bank run.