[damptowel]

But government spending within the national economy is not income constrained, so raising taxes is not a requirement.

[gozur88]

Then why do we have taxes at all?

[dTal]

To control the money supply. It's true that the government don't need to directly fund all spending with taxes, but if more money is issued than collected, the amount of money in circulation increases and the currency devalues. Obviously this should be avoided as the more the currency you're printing is worth, the better off you are.

So practically speaking, you do have to fund expenditures with taxes. You can't just create value out of thin air.

[damptowel]

Good question, what drives politicians I can only guess. Neoclassical economists have their heads buried firmly in the sand, preferring their a priori fantasies and pushing that as their agenda.

Taxes are good for creating currency demand (and large scale markets systems resulting from it), shaping incentives and income redistribution. It can also be used to put a brake on a bubble economy.

[dionidium]

It's a good question, but it's clearly not merely to raise money. They print money.