It's not that bitcoin is dangerous or something. The reason that many countries do not promote the use of the bitcoin is their own political problems. The very nature of the bitcoin makes it decentralized. And this is one of the major reasons why the governments of most of the countries don't really want to make any regulations regarding bitcoin or accept it as their legal tender. They don't want it because they cannot control it completely and this would make them accountable for any wrong that happens over the crypto market. but if it is not under their control how would they be able to resolve such kind of issues or scams. So regulation is a tedious job and most of the governments are not yet ready to do it.