In the part of the world that there are no internet it is difficult for cash money to be extinct ,because you can only use this bitcoin when you are connected to the internet, and there will be enough signal that can cotter the need for the connectoin nd some transactions.
You are right there dude Not some almost all of the Third world country has slow internet connection and sometimes they don't have in some part of their respective country. This can be really devastating on their economy if they will implement the use of cryptocurrency on their own.