There are many reasons why bitcoin is not accepted by some countries. Bitcoin, for example, is used by some criminals as a way of dealing with crime. Some officials have used bitcoin to transfer money, so some countries have banned it.
I agree with you that there are many reasons why until now some countries is still not supporting bitcoin, first of all is the bitcoin is can surely affects banks in the future so a lot of countries is afraid when it happens and some countries are afraid that bitcoin can be able to used by some criminals all over the world.