Its just protection law. I dont know about Iceland and Vietnam, but Russia and especially Bolivia have high inflation of their currency, so it makes sence for any country in trouble with their currency protect it so people canot use more sound option to keep their wealth in - bad for people, but it keeps the concept of national currency as only viable option intact even in such hard times when it must be clear even for the average person its not worth keep fiat longterm because of such high inflation.