Until now, Bitcoin is hardly accepted by countries for what it is because it is [1] beyond their comprehension, [2] a threat to their existing fiat system, [3] is neither issued nor directly monitored or supervised by the government, [4] is not owned by a certain person or company which the government could easily communicate, convince, or even threaten when the necessity arises, [5] is somehow anonymous, [6] and so forth. Having mentioned all these reasons, it is really difficult for Bitcoin to be accepted as legal tender in any country.
Yes these points are the main reason why some of the countries does not accept bitcoin and discourage their citizens from using it as we have seen so many instances wherein bitcoin has been used to extort money for unlawful activities which has portrayed bitcoin and it's anonymity in poor light, it's not easy to convince governments that's there were crimes and similar unethical activities even before the existence of bitcoin as they think bitcoin has made it easier for criminals to carry out activities.