Fiat are issued with registered numbers and recycles in the name of new currency, making the old obsolete.
i.e. They never get destroyed even if the physical notes gets burned and decayed.
But bitcoin are totally different, they can be lost
- sending to unsupported address
- loosing private keys
- people dying with private keys, etc.
Which will keep on decreasing the total available supply of the coin. making it more scarce.
Won't that bring a problem the the economics, no coins left to trade situations?