Every country has a law and has regulations to be followed.Maybe the one who is leading a country that banned or give punishment if people uses bitcoins dont like or see bitcoins as a threat to his country.
Maybe the leader himself is not open to changes or open to innovations because Bitcoin has changed the way transaction works and how it possibly can change how we transfer money from one place to another.
Bitcoin is threat for current system. Some government's think just about making profit on peoples back, with many taxes high prices they hold their power, and that is how they rule the country. They already know how to control the supply of money in the state, with that they control everything, can you imagine what is bitcoin for them now?
Countries that think about future, and about people are open for bitcoin because bitcoin is future, others that do not support bitcoin are the countries where leader's think just about their well-being.
I don't think it is a threat, the government are still powerful and they can regulate the usages of bitcoin to do it
in legitimate transactions only. If they cannot regulate it, that is the time to ban it, but I'm sure they can regulate it.