Then there is no need for our tax dollars?

I think there is a piece missing. Who in the US can lend such large amounts of money to the government? Well another government that takes their citizen's taxes probably could loan large amounts. Not you and me. I don't own bonds, or pension funds or institutions.

The filthy-rich are the ones who loan money to the government because they are taxed at such impossibly low levels. Each tax cut adds more money to the filthy-rich's coffers and pushes the tax burden further onto the middle class and poor. Now governments have to keep borrowing because they aren't taxing the people with all the money.

So the filthy-rich get tax cuts, loan that money that would have been tax money to their governments, then get interest on what should have been paid out in taxes. It's a win win for the filthy-rich. It's a lose lose for everyone else.

The funds to pay taxes and buy govt securities come from govt spending (or lending which is a subset of spending but to acquire financial assets).

“Govt debt” is akin to a savings account at the Fed, as the Fed is the U.S. Treasury’s fiscal agent.

On the gold standard, govt securities functioned to delay convertibility, with the yields a function of what it takes to get someone with a dollar to not demand gold with it.

Today govt securities are a relic, and previous to interest on reserves (banks’ checking accounts at the Fed) the only tool available to pay interest to set positive interest rates.

If we allowed the Treasury to overdraft at the Fed, there would be no reason to issue govt securities.