Bitcoins operate off central Banks meaning the government can not control its supply or influence its value like they do with fiat currencies. This threatens their ability to manage national income. Also since Bitcoin can be pseudonymous, the government worries that people may use it to evade taxes, launder money,Or finance illegal activities.
Why are some embracing it while others seek to regulate or restrict Bitcoin??
I have a pretty simple answer to this, which is that Developing Countries accept Bitcoin for the sake of their country's future, while Developed Countries accept Bitcoin with the aim of controlling it "indirectly". If we talk about governments being concerned about people who evade taxes, launder money, or finance illegal activities, then I think that's just an excuse for them to get the truth, when in reality we don't know what their plans are for that, while on the other hand I think many people already know that there is a government that finances illegal activities, such as financing a war for a group or country, and this is more than illegal activities, namely massacres, IYKWIM.