The purpose of double criminality is the basic principle underlying extradition. A country does not want to send somebody from their territory to another territory to be prosecuted for something that they don't consider to be criminal. If a country has an offence that we would not recognize in criminal law, we wouldn't extradite somebody for it, and vice versa. This is applicable all around the world. All countries apply this principle of double criminality to extradition. It doesn't matter if you have exactly the same offence; it's the conduct we look at. If what the person did would be considered criminal in your country, then that will satisfy double criminality and will allow for the possibility of extradition.
On February 4th, 2020. See this statement in context.