I suppose that this is connected with the fact that it contradicts the interests of the current governments and deprives them of control over financial flows. By allowing citizens to freely use bitcoin, i.e. an uncontrolled financial system, the means of control over citizens are lost, and therefore, power is lost. Also, in this case, the incoming taxes will fall, because traditional money will be used less. The same thing happens with exchangers. As soon as the governments prepare the legislative base (how much and for what to pay taxes), then exchangers will be allowed for use, but of course, these will be exchangers controlled by the governments and exchange will be possible only in similar exchangers. That is, as soon as the governments decide how to regulate this niche, then such actions will be allowed.