In essence fiat money or digital money is a means of payment, the only difference being cash/non-cash transactions and technical problems in payment. So far, fiat money has really helped the community in making transactions because it is easier to carry and has a different value for each sheet, fiat money supported by cash transactions is still commonly used and all levels of society like it. Meanwhile crypto needs internet access to make transactions, and it needs to be underlined, not all people understand how it works.
Fiat will always be there because it is supported by the government, try to imagine if fiat was replaced with crypto, how can rural residents who are not covered by internet access use it when making transactions.