The government and the banks won't allow the system of digital currencies to rule the world. Even if digital assets are more efficient, low cost and more secure, they won't allow it to happen simply because they have no control over it. And in the future for sure, cryptocurrencies like bitcoin will be the most effective form of doing financial transactions.
Banks really disagree with the existence of bitcoin. they consider this to be their competitor because of the blockchain that makes every transparent transaction able to create a new system that is more trusted.
Implementation is almost certain that each country will be different because not all countries can accept it as a legal payment instrument or even no recognition. although crypto is actually easier to use. because regulations are still not comprehensive, there are still difficulties in their implementation, so there will still be some obstacles.
I don't think bitcoin is easier to use during the adoption process and regulations have not been made for bitcoin. as long as there is no regulation and the ban is still everywhere, the use of crypto will certainly not be as easy as using fiat, bitcoin will not become the leading currency if the legalization of bitcoin has not occurred