Yeah, well i think chinese, russians, bulgarians, mexicans and albanians will fill in the holes.
The mafia is like a secret state within the state. And just like a state it is mainly motivated by money and power. I think organised crime is increasingly a part of legit businesses. For example a lot of the cloths sold in America comes via the camorra in Naples.
The whole russian economy is supposed to be run by gangsters. The owner of Chelsea, one of the biggest soccer clubs in the world, Roman Abramovitch, consolidated his power in the 90ies amidst 100s of assasinations. The assasinations stopped once he had gained controll.
It is usually a sign of weakness when the mafia commit violence. The violence is usually an attempt to consolidate power. Or its vendetta, retaliation against people who are trying to reduce your power by violence.