Of course I believe in fiat. I use it daily and so does everybody else. However, I do not believe in the people/institutions that control fiat. It was a lot better when fiat was tied to gold reserves. Now we just create money out of thin air, which will have severe consequences in future.
There's no reason not to believe it's already part of our daily lives and without fiat we can't get the things that we need with our daily living. But the good thing here is that we also have another option and help from bitcoin so at the same time we have chance to use these two types of currency freely.
Fiat has been a big help in the society and in the economy, it makes the life easier in a way that is has been our medium of exchange in many things.
So, let us know all forget that, we've been benefited its usage, and I don't think that no one is using fiat nowadays. Although, bitcoin is booming now still fiat exists in many ways.
If you see that current price of Bitcoin is seen on fiat currency so it is obvious that fiat is the main currency whose value is their and only through fiat currency you can live and do expenses of your family , because still bitcoin is not the main currency used for daily life expenses so we have to still rely on fiat currency for our daily life expenses. Until Bitcoin dont become main stream currency of life fiat currency value wont decrease.