There's tax-exempt bonds. You get lower interest because you're loaning to the government. State, federal, local.

There are the usual exemptions and deductions. They're mostly not means tested.

Then there's what is stated in the OP but overlooked by readers. It's US federal income tax that they aren't paying. A lot of those tax returns shown tax payments to other governments. If you pay elsewhere, there's often a credit against payment. Interesting means of tax-avoidance--paying taxes. (Then again, I don't know of anybody who doesn't engage in tax avoidance. I certainly do. I take various deductions that are option. Standard deduction for me and dependents. Child care deduction. The $1000 deduction for my kid. All of these are designed to help me avoid paying taxes. All are optional. If all tax avoidance is bad, then I guess all DUers should avoid deductions from income, income taxes and reject refundable tax credits.)