Very simple op, it is because some countries are scared that many people might use Bitcoin to launder money. Also, banks can not control Bitcoin, and most importantly is that Bitcoin is not formally linked to any of the existing laws and regulations of any central government here in the world today. So yeah, that is why I think most countries do not support Bitcoins.
It is not about countries being scared of what it brings. Let us focus on the word "support" why do you think a country will support something that is decentralized in nature? Which is the complete opposite of what a government has a right to do. When you think of it most countries does not even care that Bitcoin exist in which almost all of them are neutral about the topic. Bitcoin as of right now is not yet a threat to these countries.
Mostly because its a decentralized currency with no rules or tax laws. Government aren't kinda scared actually, they are just preventive about disturbing situations. As of India, its being heard that laws and tax will be implemented.
Moreover, many countries have other situations to control first, more important than Bitcoin probably. They might also accept if all the other countries will do so.