> Taxes don't make sense in a fiat system where the government could just print as much money as it needs anyway
There was an interesting discussion of this is a book my income tax professor in law school recommended to those who were interesting in the theoretical and philosophical issues of tax systems.
The usual argument against the government printing money is that it causes inflation.
Suppose, for example, you have a $1 000 000 000 000 in circulation. Each dollar is worth 1/1 000 000 000 000 of the value of the total economy.
If the government prints, say, $52 631 578 947 dollars, there is then $1 052 631 578 947 in circulation, each dollar now worth 1/1 052 631 578 947 of the total economy, and the government having 52 631 578 947 of those dollars, giving the government 52 631 578 947/1 052 631 578 947 of the economy, or 5% of economy.
In many ways this is very similar to a 5% flat tax, except there is no need for taxpayers to file returns, no need for complex regulations about what is or is not taxable income, and you can't evade it by keeping your transactions off the record.
From an individual point of view, losing 5% of my purchasing power to inflation isn't really worse than losing 5% of my purchasing power to taxation.
Inflation has another problem, though. As the value of a dollar, as a percent of the total economy, keeps going down, people need more and more of them to get the same things. We'd have to be frequently changing prices, changing pay, and changing everything else that is denoted in dollars.
That was probably a bigger problem in the past, and will be a smaller problem in the future. As more and more transactions go entirely electronic, we could probably internally do everything in some sort of pseudo-dollar that's pegged to a fixed fraction of the total economy or something like that that the electronic systems convert automatically to current dollars on the fly. So you go to the store to buy bread, which the store internally priced using pseudo-dollars, and the electronic price display tag under bread on the shelf converts that 2020 dollars and displays that.