Bitcoin cannot be the number one currency in the world to used by all, because it's decentralized and no government will accept it since they will not be able to control it. Government only embrace what they control and that's why they came up with fiat currency where they are in charge to do the printing of fiat whenever they want.
However, due to the increase in value of bitcoin overtime, majority of people holding bitcoin wouldn't want to use it as a currency but as an asset in order for them to make profit from it in future. If there is fiat as the second choice of currency, why will I use my bitcoin to pay for goods and services. the world is centralized and a centralized currency will always dominate.
Definitely agreed that bitcoin can not be the central currency in the world and my main reason is the total supply and of bitcoin, although it can be divided into smaller units (satoshi) it still wouldn’t be enough considering that those holding will be keeping the hold of theirs too and that will limit the supply in circulation more, so having it as main country’s currency will not be looking possible in my perspective,
As for using bitcoin as payment method I don’t think it has any reason why it shouldn’t be used, this is not by any chance going to affect you holdings, one can simply have a some bitcoin holdings and then some more bitcoin for payment, it doesn’t change anything.
Spending btc is stupid as fuck so far.
Buy and hodl works.
Buy and spend is doing the other person a favor.