I disagree unless you're talking about 'fiat' as in cash only. Compare the speed of SEPA transactions, international bank transfers (et. al.) to Bitcoin transfers, and you will see how superior it truly is.
I was pointing at doing daily shoppings in physical stores. In that regard, fiat through cash, or fiat through payment via NFC with phone or bank card are superior. Benefits are that everything is instant, no fees involved, people enjoy insured payments, etc. If you look at Bitcoin when it comes to transferring money from one point to another, then yes, it's surely superior to what fiat related infrastructures can offer.
But nowadays if you look at the shops you will find that even in third world countries people like to use digital system of payment (for example bank cards) even in local shops which have ATM for the reason of security and as these cards are from banks so they have a good fees. In that case if people know about bitcoin then they will adopt it for their shops because bitcoin is a digital currency with digital way of payment and do not involve any third party and is available with lowest fees.