of course fiat is necessary. because fiat is more or less safer currency comparing with other alternative currencies such as crypto currencies. they are mostly backed by governments and also easy way to make payments.
Yes fiat currency are still important. And in some place they are more important then that of digital currency and cryptocurrency. Cryptocurrency are not a global currency, it ban in many place and many people still doesn't use it. And it is an independent currency so their is no stability in its price. In the other case fiat are world wide accept and it has more stability than that of cryptocurrency. Cryptocurrency currency are only use digitally so in those places electricity or Internet not available in those place you cannot use cryptocurrency but fiat currency you can use any time anyway. And people have more trusyon fiat currency than that of cryptocurrency.
Yes, at this time Cryptocurrency almost does not have the talk in the whole world and Fiat is the most popular and familiar currency unit in most places of the world. No one can deny the convenience as well as the modern that crypto brings to us, but compare to fiat currency, crypto covers much risky than fiat because its extremely volatile and it almost does not have stability. Moreover, people are accustomed with using fiat in their daily life and many people are not aware of cryptocurrency or they even dont give any trust for digital currency, they just believe in something that is real. However, if cryptocurrency is recognized officially in the future, its completely more likely to replace the function of fiat.