While all countries around the world are accepting cryptocurrencies and blockchain as a new technology, then why the Asian countries like Bangladesh, India, Bhutan are against it? If they won't legalize it right now, then it would be their loss. Because in the future they will find every company in the world is accepting Crypto at that time they have to legalize it.
Your mentioned three countries are located in South Asian zone and recognized as developing countries. In developing countries, there are many problems like money laundering, corruption, unemployment, uneducated etc. Money laundering is the main factor here that the bad people will use this way and it will be difficult to identify them.