The use of these cryptocurrencies is still limited and only 15-20% of the population is dealing in this business or is aware about the market and technology and if the question arises like replacing of fiat by crypto dont seems possible at some point because fiat has gained faith of large population from the past and is widely used and because it is legalized by govt. they can exchange it easily for goods which is not the case with altcoins.So fiat gain dominance over other coins in all aspects and remains ahead of it.