I have got a good point on that.
in my opinion, crypto / digital currency will replace the fiat currency one day.
At least if everyone uses cryptocurrency for an investment place or payment instrument, I just doubt the way they buy cryptocurrency? Until today someone who has a cryptocurrency always uses money fiat to buy cryptocurrency, rarely do they exchange an item for the cryptocurrency.
So as I have confidence if money fiat will always be available and used as the first instrument of payment, then they will use the cryptocurrency as the second instrument for payment tool.