A modern society always needs a means of exchange. Gold and silver have always been accepted as such. Barter is horribly impractical so you need an accepted item to ease the exchange of goods. Almost impossible to arrive at an equitable trade using barter. How many eggs equal a gallon of gas? Imagine everyone having to make these judgements on all the of items they would trade on a daily basis.

But that is assuming a complete collapse occurs. More likely after hyper-inflation destroys the confidence in the currency a new currency will be issued backed by something of value. Usually gold or silver in order to increase the confidence and acceptance of the new money. As time goes by the metal backing of the currency will be withdrawn and the whole cycle ends in a crisis again. Just think of holding gold or silver as insurance that you hope to never have to use. But just look at Venezuela today and you will see a real-life example of the value of gold and silver.