One basic reason why it is a good idea to have a centralized currency is that this allows governments some amount of control over inflation, which is good if you're living in a country where the government has at least some incentive to make decisions that benefit its population
What a load of crap.
De facto the US controls interest rates globally and most countries have no choice but to follow US rates in order to keep their currency at a somewhat stable exchange rate against the USD. That in turn is crucial for their economies especially if they trade with the US, which basically every country does. Since the FED fully controls the US interest rates, it effectively controls the interest rates of other countries as well, at least for those countries having a non-trivially sized economy, severely limiting other countries' capabilities to control inflation. The US doing QE? Other countries have no choice but to follow suit.
Zooming out and ignoring bumps in the chart, it is apparent that nominal US interest rates have been on a downtrend since the the eighties. In the past 40 years the US interest rates have been gradually going down from 15% in the eighties to near zero today. At zero the nominal interest rate cannot go down much further, but the real interest rate can by pushing up inflation. Indeed, the real interest rate is by some estimates a negative 5% as inflation starts to pick up steam due to QE programs.
The effects of low and negative interest rates are currently increasing the wealth gap between people and countries. Those with assets or high incomes are able to take advantage of near-zero interest rates by getting loans basically for free which enables them to buy (more) assets such as real estate and stocks, inflating their prices. Those without assets or low incomes do not have access to these loans and just see prices around them increase while their salaries stagnate. The Cantillon effect is real and currently manifesting itself increasing the wealth gap on a global scale.
Sure, governments have an incentive to serve their population but only to the extend that they remain in power after the next elections. This gives governments a myopic 4-5 year time horizon which is especially damning for the US being the country that is de facto in control of global of interest rate policies. At some point, real interest rates cannot go down any further and when the point comes at which financial markets become uncomfortable with the US debt levels interest rates will need to rise to support the USD. In the short term, rising interest rates will likely lead to financial instability and defaults of countries and companies that have come to depend on near zero rates however, resulting in a deadly negative feedback loop of defaulting companies and countries while US interest rates keep going up to support the USD, pushing up interest rates all over the world in its wake. Lower interest rates on the other hand keep up the appearance of a blossoming economy with inflated stock prices, inflated real estate prices and low unemployment caused by all the misallocation of capital. There is no incentive for any US administration to end this facade and start taking the inevitable economic pain today by starting to do what is needed which is increasing interest rates because it would totally destroy them at the next elections.
There is only one asset in the world which operates outside of government control and manipulation, which cannot be arbitrarily inflated and which is practical to use as a money, and you may have guessed it, this asset is Bitcoin.