state wants to get tax. the input and output of the money can not be controlled. also a serious competitor for bankers. also a good way to make money. countries are opposed to it. a money they can not control is troubling governments.
maybe on the one hand, that's why there are several reasons why many countries refuse the use of crypto and bitcoin currencies, there is one more thing that might make the government reject crypto currencies is that they are not ready to apply the technology used by crypto currencies