You being a member asking this question sounds a bit dumb, quite simple, all country's have their own currency, centralized currency, fiat controlled by their governments. Isn't it obvious why Bitcoin was created, decentralized currency, not correlated to any other fiat currency/assets (to an extent) or restricted to any country or government or monetary policies and can be used globally as a medium of exchange, standalone decentralized currency.
What is the real and context of this question