Te very first time individuals know is bitcoin, so the existence of bitcoin money will be described as a bitcoin imitation. I'm certain bitcoin money will be the same as altcoin and individuals make main concern is bitcoin.h
Yes the users of bitcoin are not much but increasing with a faster speed and I do not think that there are countries which do not allow their citizens to use bitcoin but almost all of the countries are open to the usage of bitcoin. Only a few countries has banned it in their countries but now they found that it is beneficial to use bitcoin so the citizens of that country are using bitcoin.
You can using Bitcoin for online payment, but you can not using Bitcoin as a payment method in reality as FIAT. The government manage the country's economy through FIAT system, use Bitcoin will make them get more troubles and the criminial can take advantage this problem to break the law.
Yes criminals can take advantage of it but criminals can also take advantage of real life money and we do not do anything about that? why should the government do anything about bitcoin just because it is used by criminals that is unfair against the people who do not use it for bad stuff.