If it were the case that the main currency of every country in the world is Bitcoin. Then how do you think the world economy would be run? Because when Bitcoin becomes the main currency, the American dollar and other countries will have Bitcoin as their main currency. The local currency of that country will be associated with it as the second currency. In this case, how would Bitcoin be used or how can it play a good role in the world economy?
Do you know the reason behind the name Digital Gold? I don't think you know, because bitcoin will never be a world currency, maybe a world currency in another way but it's not going be a main currency for the world. It's digital gold because is more like gold used for reserve for many countries, infact from the onset it's meant to be an alternative currency so the illusion of bitcoin dominating fiat is a facade.
It's always going to be a big deal to hold but it's not going to be a currency to be spent like fiat, the world runs in cash, debt bitcoin isn't debt so it can't be used for controling the masses. fiat is meant to keep the suppressed in a continuous suppression.