The fact El Salvador accepted Bitcoin as a legal currency does not mean that other government across the world will accept it someday. The reality is that , the government will keep fighting bitcoin with all market strategy and strick regulations.
Reasons why they will keep fighting is not about the prosperity of the people majorly but about power and authority to control people. This is why they prefer the centralized system in order to keep the people poor so that they can run to their feet for daily bread, seek shelter and wait for other provision.
We all know that through Bitcoin, every one will be there own boss. No control or submission to any authority over your own belonging or money, the life threatening taxes will be done away with.
But as of now, no matter how popular Bitcoin becomes, it will keep facing the wrath of the angry government who need to keep people poor.
More also, before bitcoin will become used by everyone across the world as means of payment, most users hear must have grown white Bear,
Bitcoin is characterized by its own characteristics. Governments of any country consider it a challenge because of this unique feature. Because it is free from central control due to which the power of money is spread directly to the people rather than from the center. OP as you say El Salvador recognizes Bitcoin as a legal currency and they are doing well economically. So the rest of the world doesn't accept this system easily. Because its financial system is not under the control of the government.
Despite the thousands of restrictions imposed by governments around the world, Bitcoin's massive popularity and people's freedom to act as a platform can bring major changes to the economy of the future.
Finally, Bitcoin is a decentralized digital currency that is transacted among people without the control of any central government.