Their countries , their laws. It really depends on your definition for not supported too . If we speak about banning then as far as I know I don't think there is a country that actually banned bitcoin , at least nothing official and If there is then Its related to the banking system with one way or another . If its about the lack of usability in ATMs , local shops then there are plenty of countries and It takes time as some countries have more priorities .
Actually, in 2014, the central bank of Indonesia considered bitcoin as an illegal medium of payment. While it was not really banned, meaning, those who would want to use it are free to do so without the fear of getting punished, the use is still considered restricted.