Why Will Fiat Currency Always Exist?

The truth is that fiat currency is such an advantage that a people cannot compete without it.

Competing currencies and commodities exist but they are not anywhere near as price stabilized as fiat money CAN be.

So we are always going to have it. Probably digital will replace it and it will have to because the abuse of it has gotten out of hand.

What real purpose does government debt serve over simply printing money and paying with it?

You pay the price of interest in order to delay the equlibrial neutrality of money working through the economy.

In other words, the faster new money moves the faster prices in the existing cycle of production adjust.

Fast adjustment is bad if it interferes with production ( planning ) cycles.

So instead we pay interest and sell government debt so that we inflate away the interest at about the same rate that prices adjust in the economy.