Customers use currencies if it lets them buy stuff. Shops accept currencies if people come and want to buy stuff with that currency. In touristy places, it's co

Customers use currencies if it lets them buy stuff. Shops accept currencies if people come and want to buy stuff with that currency. In touristy places, it's common to see people list their prices using currencies from common originating countries, regardless of the legal currency in that country. Any new thing needs to be better than the current thing at least in one domain, if it wants to grow users. Fiat currencies work so well, that the only niches cryptocurrencies can find is crimes really, avoiding financial sanctions, etc. Like China for example bans their citizens to trade the chinese currency for foreign currency (above small limits). Then buying bitcoin domestically makes sense if they don't trust the chinese government to keep their own currency valuable. Of course, all the exchanges operating in countries where there is reasonable laws require KYC to be in place. Cryptocurrencies are also in many ways more trackable than non-crypto currencies. So for crime it makes no real sense to use most crypto currencies.