People will have to wait too long for transactions.
We don't have very developed network yet still we face this problem but only on a smaller scale.
if people will use credit/debit cards then there are many people who will use only paper money as everyone cannot afford to have credit totally depends on bank procedures, but the majority of the people will continue to use paper money.
Basically, paper money is the main thing used by everyone. Because it is only with paper money we can get something that can not be obtained by with other currencies such as cryptocurrency. Because it is now cryptocurrency can not be used like banknotes, but for investment cryptocurrency is very supportive to get many benefits. Because now cryptocurrency has been ogled by most people, so the higher the price and certainly provide many advantages. Because the system is very good and profitable.