1. Internet every where is not yet done.
2. Awareness with Crypto ( but its not a big thing, as most are aware of how to use currency. )
3. Bitcoin is only 21,000,000 and world population is more. ( This can fix by other altcoins same like USD/RUB/CNY etc )
What other difficulties we can face ?
The first 2 problems are the ones I see that would create a big problem for the complete transition to the digital world because in the case of number one, even if there is internet everywhere, there are still some people who will not use it no matter the explanation due to either cultural inclinations or religious connotations. Today in some parts of the world, some people don't still wear cloths or shoes despite the amount of years civilization have occurred. Going to number 2, the awareness will be something that will take forever to be done because it will mean the complete reorientation of people about the financial system right from the time that children know that there is money not living behind the senior citizens whose way of life has been about the normal way we have been doing things.
The irony of the matter is that, this set of people cannot be left behind because some of them are our grandparents, parents, kinsmen, etc whose population is significant in age distribution census of the country.