Fiat money is money that is guaranteed to the State, of course I never hesitate. the use of the bitcoin I think only as an alternative, fiat money is still the largest and can not replace by any included bitcoin.
Yeah that's true fiat is really old and it has been around for more than 500 years while bitcoin is just a 8 year old digital currency which currently has many flaws which can affect the use of it in daily life while fiat is instant as we don't need any sort of confirmation and it is widely accepted anywhere in the world.
Fiat is still a very important part of our life and without it i think it is very difficult to lead a normal life as we still mostly depend on bitcoin for most of the activities and that is the reason that still bitcoin is one of the most important part of our life.