Why we can use Salesforce Multicurrency?

Adds the ability to record amounts in different currencies. If you don't have multicurrency enabled, then amounts are just displayed as an amount. Allows amounts to be converted, displayed and reported according to exchange rates. Allows the use of dated exchange rates so the value at a certain time can be fixed

When there is a business that is operating in multiple countries and their currency is different, in that case, we can opt for multi-currency to have the business process being managed as per the currency of the country or location.