yesterday i heard that using of bitcoin illegal in Taiwan i don't guess why in some country its legal and in some like Taiwan is illegal?
We can not blame Taiwan or other country who banned bitcoin or announce that it is illegal in their country. Because some country wants to avoid some illegal activities inside their country thats why they banned bitcoin. Admit it they can use Bitcoin in any illegal activities which is wrong because we are all suffer if many countries will banned because of that doing.
Speaking of using a currency that is used for illegal act then I'm not sure one of the way they use bitcoin. All currencies can be used for illegal act without being known by the government or by other people, moreover money fiat use is more dangerous if used as an illegal payment system because it cannot be tracked by anyone unless the person who make the transaction tells to others. So, I am quite doubtful if a government decides to ban bitcoin just because it can be used as an illegal payment system while money fiat itself can be used easily to do that.