So they can allow to invest and trade in stocks markets but not in cryptocurrencies that is not fair and unacceptable.
They don't think it is harmful for their economy or for their country citizens. actually most of the countries rejecting cryptocurrency related bills due to anonymous factors but truth this most of the politician doesn't want cryptocurrency to be act as main mode of payment it in the government banks or any government related transaction. Because if that has been done via crypto payment they will not able to to do the corruption kind of things and make money out of it.
Finally greediness of money is the matter for this cryptocurrency acceptance issue. Nothing more than that...
For corrupt officials, on the contrary, using cryptocurrency due to its high degree of anonymity is much better than using ordinary money.