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 .
Yes, you're right. I think there are some countries that bitcoin is being banned. Bitcoin in other countries was not legal. There is no tax in bitcoin. It is another type of currency that we can use to buy things like goods and services. But there is also countries that bitcoin was supported. Like here in my country, bitcoin was being popular gradually because its price was fluctuating. You noticed that the value of BTC every minute is shifting.
Lack of usability in ATM's? I think people would choose ATM's for the fastest transaction of money. But in terms of bitcoin, It could also be saved it to your wallet and you can cash out whenever you need money.